The world beneath the ocean’s surface offers stunning visuals, vivid colors, and rare encounters that make underwater photography an addictive pursuit for enthusiasts and professionals alike. However, capturing the magic of the deep requires more than just a capable camera; it demands reliable, user-friendly underwater housing that can function effortlessly under pressure. The Fantasea FRX100IV housing, specifically designed for the Sony RX100 IV and RX100 III, is one such product that has attracted attention for its robust build, thoughtful design, and affordability.
Crafted from durable polycarbonate and packed with essential features like double o-rings, an internal moisture detection system, and compatibility with a range of wet lenses, this housing is designed to meet the needs of a wide spectrum of underwater shooters. Whether you’re a first-time snorkeler wanting to document your reef explorations or an experienced diver capturing complex macro shots, the FRX100IV promises to deliver strong performance without breaking the bank.
In this first part of our comprehensive review, we’ll cover the background of the camera-housing pairing, initial impressions, technical specs, and a deep dive into its ergonomics and control layout. We aim to uncover not only the strengths but also the limitations of the Fantasea FRX100IV so you can make an informed choice for your underwater photography gear.
Understanding the Sony RX100 IV: A Compact Powerhouse
Before diving into the housing itself, it’s important to understand why the Sony RX100 IV is a popular choice among underwater photographers. The RX100 IV combines portability with professional-level image quality. It boasts a 20.1MP 1-inch Exmor RS CMOS sensor, capable of capturing ultra-sharp stills and stunning 4K video. It also includes advanced features like super slow-motion video, fast hybrid autofocus, and manual control options, all packed into a pocket-sized frame.
Its sensor size and image quality set it apart from other compact cameras, while its dimensions make it an ideal candidate for lightweight travel rigs. For those who value portability without sacrificing image quality, the RX100 IV is a compelling choice. Naturally, to fully utilize its potential underwater, a housing like the Fantasea FRX100IV becomes a necessary investment.
First Impressions: Build Quality and Design Language
When first handling the Fantasea FRX100IV, one immediately notices its compactness and lightness. Constructed from a clear polycarbonate plastic, the housing weighs just 600 grams (without the camera), making it among the lightest options for the RX100 series. The transparency of the rear panel offers visual reassurance—you can easily check camera alignment, verify control engagement, and inspect for any leaks or issues inside the case.
The build quality feels solid for a plastic housing, with a snug fit that doesn’t feel cheap or flimsy. The finish is matte on the front and glossy clear on the back, providing both durability and visibility. There’s a well-balanced grip on the sides and a cold shoe mount on the top that adds modularity for accessories like focus lights or action video lights.
The housing is depth-rated to 200 feet (60 meters), which is more than enough for most recreational and prosumer divers. Though technical divers may look for more specialized equipment, the FRX100IV more than meets the depth and durability expectations for typical underwater adventures.
Control Layout: Mimicking the Sony RX100 IV
One of the standout design achievements of the FRX100IV is its commitment to ergonomic fidelity. That is, the external controls on the housing closely mimic the RX100 IV’s actual buttons and dials. This might seem minor, but it eliminates a major pain point for divers: relearning control layouts underwater.
Each button on the housing is clearly labeled and well-placed. The shutter release is a vertical push button, ergonomically situated for ease of use whether you’re wearing gloves or diving barehanded. A thoughtful front control ring adjustment knob is positioned on the left side of the housing. While it requires a second hand to operate, the tactile feedback and functionality are smooth and reliable.
The rear control dial—so crucial for manual shooting—is managed through a unique spinning knob that Fantasea has integrated into the housing design. This particular feature sets the FRX100IV apart from many competing housings that neglect the rear control dial or make it difficult to use.
However, not all control placements are flawless. The video record button, though easy to reach, is a bit too accessible and can sometimes be pressed accidentally, especially when the camera is clipped off to a BCD. This could lead to unintended video clips or battery drain, a small yet noteworthy issue for divers who rely on battery life during long underwater excursions.
Sealing Mechanism: Double O-Ring Confidence
The sealing mechanism of any underwater housing is perhaps its most vital feature, as even a small leak can be catastrophic for your camera gear. The Fantasea FRX100IV offers a double o-ring seal, which adds an extra layer of protection over many housings that rely on a single o-ring. This redundancy significantly reduces the chance of flooding from misaligned or dirty O-rings.
To open the housing, you first press a plastic safety lock tab and then twist the side-mounted latch. At first glance, this mechanism may not appear as robust as metal clamps or twist locks, but it performs well in practice. It’s also easy to operate, even with cold or gloved hands. Once open, the camera is cradled neatly into position by a clever spring-action LCD skirt that aligns it perfectly with the external controls.
There is no need to screw or unscrew the camera from a tray, a convenience that saves time during battery swaps or memory card changes. Unlike many other housings where removing the camera feels like coaxing a fragile object out of a stubborn shell, the FRX100IV allows users to lift the camera out easily using their fingers—no shaking required.
Built-In Moisture Alarm: A Welcome Guardian
Another feature worth emphasizing is the moisture detection system built into the housing. The sensor is strategically positioned at the lowest point inside the case, where any ingress of water is likely to collect first. This proactive placement ensures the earliest possible warning in case of a leak.
Once triggered, the moisture alarm produces an audible and visual alert, giving divers a chance to surface and save their camera before it’s fully compromised. While experienced underwater photographers often add third-party moisture detectors or silica packs as an extra layer of caution, having a reliable built-in system is a significant advantage, particularly at this price point.
In-the-Box Accessories and Expansion Options
Fantasea doesn’t just sell you housing; they provide a starter kit to help you get in the water quickly. Included in the box are a hand strap and a flash diffuser, both of which are practical additions. The hand strap is sturdy enough to secure the housing during shore entries or boat dives, while the flash diffuser improves onboard flash performance in macro scenarios.
Additionally, the housing includes a lens port adapter compatible with M67 mount wet lenses. This opens up a range of shooting opportunities—from super macro to wide-angle landscapes—without having to invest in a different housing system. The ability to use popular lenses such as macro diopters and wide-angle conversion lenses gives this housing significant versatility for underwater photographers looking to expand their creative options.
Customization and Modular Setup
While the FRX100IV works well as a standalone, handheld setup, it truly shines when integrated into a modular system. It features threaded mounting points for trays, arms, and strobes, making it compatible with most third-party underwater photography gear.
If you prefer shooting with external strobes, dual-arm setups, or constant video lighting, this housing allows for effortless expansion. Many divers have built out rigs using the Sea&Sea YS-03, Bigeye M67 Wide-Angle Lens, or Bluewater +7 Macro Lens with excellent results.
This modular flexibility means the housing can evolve with your skill level and creative ambitions. What starts as a simple point-and-shoot dive rig can grow into a serious underwater imaging system over time.
By the end of this first examination of the Fantasea FRX100IV housing, it’s clear that it is designed with thoughtfulness and attention to real-world diver needs. It offers more than just protection for your camera; it actively enhances the underwater shooting experience with reliable controls, safety mechanisms, and expansion capabilities.
To summarize some key takeaways from this section:
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Ergonomic control layout mirrors the RX100 IV for seamless operation
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Double o-ring design improves water-tight reliability.
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Built-in moisture detection adds peace of mind.
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Easy insertion/removal of camera—no tools or trays required
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Compatible with wet lenses and external accessories
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Lightweight and compact for travel convenience
Taking the FRX100IV Into the Water
Once the housing has been tested in the lab and its mechanical features evaluated, the next logical step is to examine its performance in real-world underwater environments. Testing a housing in actual dive conditions reveals how it handles under pressure—both literally and figuratively.
When submerged, the Fantasea FRX100IV housing delivers a dependable and user-friendly experience. Its ergonomic design translates well underwater, where ease of access to camera functions is critical. The clearly labeled buttons remain easy to identify even in low-visibility conditions or when wearing thick gloves. The physical feedback of each control button is reassuring, letting the photographer know whether or not a command has been executed.
Whether diving in tropical reef systems, colder temperate waters, or deeper offshore sites, the housing maintains structural integrity and remains comfortable to use. The lightweight design is also helpful for long swim-throughs, drift dives, or scenarios where a heavy rig might fatigue the arms over time.
This part of the review will delve into the underwater performance, including handling, control access, image sharpness, video capture, buoyancy, and lighting compatibility. We will also examine real-world feedback from underwater photographers who have relied on the FRX100IV across different ocean environments.
Handling and Comfort During Dives
Handling is one of the strongest aspects of the FRX100IV housing. Its relatively small size and well-distributed weight make it excellent for divers of all levels. Even without a tray, the housing is manageable, though many photographers eventually opt to mount it onto a tray with handles for added stabilization and the ability to attach external lighting.
The grip surface is slightly textured, which reduces slippage even when the housing gets wet. The shutter button is positioned perfectly to rest naturally beneath the index finger, providing a comfortable and intuitive trigger mechanism. The control ring dial is responsive and can be adjusted with precision, though left-handed shooters might find its side placement slightly awkward for rapid use.
Importantly, the rear control wheel is fully functional thanks to Fantasea’s rotating knob. This opens up a wide range of manual settings adjustments underwater, such as aperture or ISO, depending on how the user has configured the camera settings.
The zoom lever is firm yet responsive, allowing smooth focal transitions without stutter. This is especially important for video shooters who want to maintain a cinematic feel to their footage. The buttons require slightly more pressure at depth, which is common in polycarbonate housings, but they never feel jammed or unresponsive.
Image Quality and Lens Compatibility
The Sony RX100 IV, already capable of outstanding image quality on land, does not disappoint underwater when paired with the Fantasea housing. The optical clarity of the lens port is sufficient for maintaining sharpness and contrast. The camera’s 1-inch sensor provides greater dynamic range than most compact systems, capturing detail in both shadows and highlights. This is especially beneficial in wide-angle reef shots, where lighting conditions can vary drastically from foreground to background.
Underwater macro shots benefit from the RX100 IV’s fast autofocus and the ability to shoot in RAW, allowing divers to extract more detail and make substantial edits during post-processing. When paired with external wet lenses like the Bluewater +7 Macro Wet Lens, photographers can achieve astonishing detail of tiny creatures such as nudibranchs, anemone shrimp, or seahorses.
Wide-angle enthusiasts can use a Bigeye M67 wide-angle lens to get closer to large reefscapes or marine life like turtles, stingrays, and reef sharks, while still keeping the entire subject in the frame. The housing’s standard M67 thread makes switching lenses mid-dive relatively simple, assuming calm conditions and stable trim.
Color reproduction is excellent, especially when using a custom white balance or shooting with external lights. The RX100 IV’s sensor responds well to ambient blue light, but photos benefit significantly from strobe use, which restores red tones that are quickly lost in water.
Buoyancy and Trim
One of the first things divers notice after entering the water is the buoyancy behavior of the housing. Out of the box, the Fantasea FRX100IV housing is close to neutral but leans slightly negative. This is beneficial in the sense that it will not float away during a drift dive or if released. However, for long dives or when using additional accessories like a wide-angle dome lens, the negative buoyancy may increase.
To improve trim and wrist comfort, many photographers add buoyancy arms or foam floats to their rig. This helps maintain a neutral balance and allows for better stability when composing shots. With proper rig balancing, the FRX100IV becomes an agile, stable underwater tool for capturing stills or smooth video.
Its compact profile also makes it suitable for tight environments, such as inside wrecks, caves, or coral swim-throughs, where larger DSLR or mirrorless housings might be cumbersome. It's reduced drag through the water makes it ideal for freedivers or snorkelers, who need minimal resistance to conserve energy and breath-hold time.
Video Shooting Experience
The Sony RX100 IV was built with video shooters in mind. It offers 4K video at 30fps, 1080p at high frame rates (up to 120fps), and impressive slow-motion modes. When housed in the Fantasea FRX100IV, the RX100 IV transforms into a compact video powerhouse.
The front lens port allows unobstructed shooting, and the housing’s controls are sensitive enough to permit smooth start/stop operation for video. However, as mentioned earlier, the record button is prone to accidental activation, especially when the camera is clipped to a diver’s BCD. This is one of the few ergonomic drawbacks of the system and can be mitigated with careful handling or a padded cover over the button.
The RX100 IV’s autofocus system performs well in video mode, tracking subjects with accuracy, especially in wide-angle scenes. For macro video, it is advisable to pre-focus or use manual focus if your subject remains relatively still.
When paired with external video lights, the FRX100IV housing and RX100 IV deliver brilliant footage with accurate colors and minimal distortion. The housing’s clear rear window also makes it easy to monitor framing and focus through the LCD screen. Divers who opt for diopters or macro wet lenses will appreciate the ability to fine-tune exposure and focus directly from the housing’s intuitive controls.
Shooting Macro Underwater
Macro shooting is one of the most rewarding types of underwater photography, revealing tiny creatures and intricate details that are invisible to the naked eye. The FRX100IV is ideally suited for macro work when combined with the RX100 IV’s inherent capabilities and external wet lenses.
Focus is rapid and accurate, and the camera's sensor offers plenty of resolution for cropping without significant loss of detail. The housing’s compatibility with wet macro diopters opens up opportunities for extreme close-up work. This is where the fine-tuned control wheel and dedicated exposure buttons shine, giving you full control over aperture, shutter speed, and ISO.
When lighting is added—especially with a strobe or focus light—macro subjects leap to life with rich color and sharp texture. The size of the housing also makes it easier to get close to shy or skittish creatures without casting a shadow or stirring up sediment.
The ability to switch lenses underwater means you can begin your dive focused on macro, and if the opportunity arises, unscrew the macro lens to shoot a wide-angle scene. This versatility makes the FRX100IV one of the most well-rounded housings in its class.
Cold Water and Gloves: Usability Across Environments
Not all divers operate in tropical waters. Cold water environments bring their own set of challenges, including thick gloves, stiffer gear, and reduced dexterity. Fortunately, the FRX100IV housing performs well even in these less forgiving conditions.
The large, wide buttons are easily operated with gloves. The shutter release has enough travel and resistance to prevent accidental firing, but remains smooth to operate. Controls like the zoom lever and mode dial are manageable even with dry gloves, which is not the case with every compact housing.
Visibility of the LCD screen through the rear panel remains clear in colder water. There is no noticeable fogging or visual distortion, assuming desiccants are placed properly inside the housing. The built-in moisture detection system is particularly useful in colder environments, where condensation can form unexpectedly and signal early signs of a potential leak.
Real-World Feedback from Divers
Several divers who have used the FRX100IV have echoed similar sentiments in reviews and personal reports. Many praise the reliability of the sealing mechanism, stating that after dozens of dives, the housing showed no signs of wear, leakage, or malfunction.
Others highlight the value for money, especially when compared to housings from more premium brands. While it may not have the build of an aluminum housing, the FRX100IV performs just as well in practice and includes thoughtful touches that reflect Fantasea’s attention to real user needs.
A few photographers pointed out the internal reflection issues that can occur when using certain wide-angle wet lenses. This can usually be mitigated with careful lens placement, anti-reflection rings, or adjusting the angle of the strobe. Some also wish the housing came with a pre-installed vacuum valve, though this can be added as a custom modification.
Overall, user sentiment leans strongly positive, especially for those who want a compact, functional system for frequent recreational diving.
Recommended Accessories for Maximum Output
To unlock the full potential of the Fantasea FRX100IV housing, a few additional accessories are strongly recommended:
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Macro Diopters (M67 mount) for enhanced close-up detail
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Wide-Angle Conversion Lenses for reefscapes and large marine life
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Dual Tray and Arm System for balance and stability
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Underwater Strobes or Video Lights to restore color and reduce noise
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Focus Light mounted to the cold shoe for low-light conditions.
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Silica Gel Packs to prevent fogging
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Spare O-Rings and Silicone Grease for routine maintenance
These accessories significantly enhance the shooting experience and allow the system to adapt to a wide range of underwater scenarios.
The in-water performance of the Fantasea FRX100IV housing proves that it is far more than just a protective shell. It transforms the Sony RX100 IV into a versatile underwater imaging system capable of delivering professional-level results in a compact, affordable package.
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Excellent ergonomics and control layout in the water
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Crisp, vibrant image and video quality with strong macro potential
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Compatible with a wide array of wet lenses and strobes
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Handles well across environments, from tropical reefs to cold-water dives
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Lightweight and compact, ideal for travel or freediving
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Best performance when used with external lighting and buoyancy control arms
The FRX100IV has proven itself as a capable performer for divers of all skill levels, offering a practical balance between functionality, portability, and cost.
Long-Term Durability and Reliability
For any underwater housing, durability is not just about surviving a few dives. It is about holding up over months and years of repeated use under varied environmental pressures. Saltwater corrosion, sand exposure, water pressure at depth, and UV degradation are all real threats to the integrity of underwater equipment. This is where the long-term performance of the Fantasea FRX100IV comes into focus.
Constructed from high-quality polycarbonate plastic, the housing has proven to be resistant to UV fading and cracking, even after consistent exposure to saltwater and sun. Divers who log frequent dives over a year or more have reported minimal wear, especially when the housing is rinsed properly and stored away from direct heat.
The double o-ring system remains one of the most reassuring aspects of the design. It continues to seal effectively over time, provided the o-rings are kept lubricated and inspected regularly. Unlike some housings where o-ring grooves wear down or warp with age, the FRX100IV’s o-ring channels stay structurally stable, offering predictable watertight closure.
Control buttons, which are mechanical and subject to salt accumulation, have shown little stiffness or degradation in function. The spring-loaded shutter and rear control dial spinner maintain their tactile response. Some minor issues have been observed with the video record button if it’s frequently exposed to sand or fine sediment, but such cases are rare and preventable with regular care.
Users who dive in cold water or silty environments appreciate the housing’s resistance to sticking controls, and its transparency makes any potential buildup or wear visible well before it becomes problematic.
Maintenance Best Practices for Extended Use
To keep the Fantasea FRX100IV functioning at its best, a simple but consistent maintenance routine is key. This prevents corrosion, preserves button elasticity, and ensures reliable sealing over time.
After every dive, the housing should be rinsed thoroughly in fresh water, preferably while all buttons and dials are activated to flush out any salt or sand. A soaking bath is preferable over running water, especially if the dive site involves silt, sand, or salt-heavy currents.
Once rinsed, the housing should be dried with a clean cloth and left to air dry with the back open, allowing any remaining moisture to evaporate naturally. Avoid exposing the housing to direct sunlight during this process.
Inspect the o-rings carefully after every dive day. If no debris or damage is found, there’s no need to remove and clean them every time, as repeated removal can sometimes cause more wear than necessary. However, they should be fully cleaned, inspected, and lubricated every few dives or when stored for longer periods.
Before storing the housing, it’s good practice to remove the moisture alarm battery if the housing will not be used for several months. Also, keeping the housing in a cool, dry environment—ideally in a padded case—prevents UV or impact damage between dive trips.
When maintained properly, the FRX100IV can deliver reliable performance for years, making it a strong investment even for frequent divers.
Comparing Alternatives: Is It the Right Fit?
The market for RX100 series housings is competitive, with several manufacturers offering options for divers with varying needs and budgets. Fantasea stands out by balancing performance, affordability, and ease of use. Still, understanding how it compares to other options is important for buyers deciding between systems.
Nauticam offers a premium aluminum housing for the RX100 IV, known for its exceptional machining, integrated vacuum valves, and more precise controls. However, the cost is significantly higher—often double or triple the price of the FRX100IV. For photographers who demand absolute precision or work in extreme conditions, that extra investment may be justified.
Ikelite produces a housing with a similarly rugged polycarbonate build, but it tends to be bulkier and heavier, making it less desirable for travel. Ikelite housings also lack the rear control dial spinner that Fantasea includes, which limits manual control underwater.
Recsea and SeaFrogs also manufacture RX100 IV housings, but they vary in terms of build quality, support, and accessory availability. SeaFrogs, for example, offers a budget-friendly option, but at the cost of ergonomics and customization. Some lack proper moisture detection or M67 lens support, which limits their upgrade potential.
Fantasea sits in the middle tier, offering a compelling mix of professional-grade controls and travel-friendly dimensions. For most recreational divers and serious hobbyists, it hits a sweet spot between quality and affordability.
Who the Housing Is Best For
The Fantasea FRX100IV housing is ideally suited for:
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Traveling divers who want lightweight and compact gear
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Recreational scuba divers shooting stills or video casually or semi-professionally
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Freedivers and snorkelers who need minimal drag underwater
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Macro photographers looking to add diopters and shoot small marine life.
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Underwater videographers want a compact 4K rig with good ergonomics.
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Beginner-to-intermediate users who want an upgradeable system without investing in bulky DSLRs or mirrorless setups
Its ease of operation and thoughtful features also make it a great teaching tool for dive professionals offering underwater photography workshops. Because it allows full control of the camera’s advanced settings, it’s an excellent bridge between point-and-shoot simplicity and full manual mastery.
It is less ideal for those who regularly dive deeper than 60 meters, require professional-grade strobes or optical fiber syncing, or are planning to upgrade to a larger camera system soon. For those needs, more advanced or modular housings may be more appropriate.
Final Thoughts on Value
Value in underwater photography gear is measured not just by cost, but by how well a system balances reliability, usability, upgradeability, and results. On that scale, the Fantasea FRX100IV housing earns high marks.
It delivers on all key fronts—ergonomics, image fidelity, safety, and accessory support—without inflating its price with unnecessary features or metal materials. It provides beginners with a straightforward learning curve while offering enough depth for more experienced shooters to grow.
The inclusion of features like the rear dial spinner, moisture alarm, and wet lens compatibility distinguishes it from basic housings. Its form factor encourages travel, and its intuitive controls reduce the learning curve for new users.
As a complete package, it feels well-refined and designed by people who understand the needs of actual divers, not just engineers.
Conclusion
The Fantasea FRX100IV housing stands as one of the most practical, feature-rich, and affordable underwater housing options for the Sony RX100 IV and RX100 III cameras. It merges a compact and travel-friendly design with robust underwater functionality, giving photographers full access to their camera’s capabilities while maintaining a reasonable budget.
Its performance in both controlled and real-world dive environments showcases its versatility. Whether capturing reefscapes, macro marine life, or cinematic video, this housing enables users to focus on creativity instead of worrying about the gear.
Backed by a thoughtful design that includes double o-rings, a moisture detection system, easy-access controls, and wide compatibility with wet lenses and lighting accessories, the FRX100IV proves to be more than just entry-level. It is a serious tool for underwater visual storytelling.
Divers seeking a dependable, upgradeable, and easy-to-use housing that won’t weigh them down—financially or physically—will find the Fantasea FRX100IV an outstanding choice. With proper maintenance and care, it’s a housing that can evolve with your skills and continue delivering results across countless dive adventures.