Originally reviewed by NEREUS Magazine (Official Publication of SUSV - Swiss Underwater Sports Association)
No Power Required? Wireless WLAN Connection Underwater Made Possible
At first glance, it sounds almost too good to be true: a stable WLAN connection between a camera in an aluminum housing and a smartphone in a plastic housing “ completely without power, cables, or active amplifiers. Yet there is a system that makes exactly this possible: Divevolk’s “Sealink.” It transforms the affordable “Seatouch 4 Max Plus” into a smart control center for system cameras.
The complete Divevolk Sealink setup showcased in NEREUS Magazine
Technically Sophisticated, Physically Clever
How can this work when metal housings normally completely block WLAN signals? The trick lies in a so-called radio frequency coupling system. Active signal amplification would only be possible underwater with a power source. Sealink, however, uses a purely passive principle from high-frequency technology.
WLAN signals (usually 2.4 or 5 GHz) can propagate well through plastic or acrylic, but not through aluminum. Aluminum acts like a Faraday cage and completely shields the signal. This is where Sealink comes in: a special cable “ comparable to a miniature waveguide “ is positioned externally on the housing so that it picks up the signal from the camera’s WLAN antenna and transmits it via an optimally constructed plastic structure outside in the water.
Key Technical Points:
- The external starting point on the housing is located where a signal emerges from the camera housing “ namely above the plastic disc of the housing, where the camera display is normally visible
- The thick cable then tunnels the WLAN signal through the water to its output, which is positioned as close as possible to the WLAN antenna of the phone in the Divevolk housing
- The result: a functioning WLAN connection through a metallic housing, purely passive “ and reliably with proper alignment
System Limitations
The whole system naturally only works under certain conditions:
Range Limitations:
- The range is very short
- Camera, Sealink cable, and smartphone must be in immediate proximity to each other
- Ideally, the two endpoints are only millimeters away from the WLAN passage
Critical Factors:
- Antenna alignment is crucial
- Cable integrity is essential “ kinks or damage can severely impair signal transmission
- The principle only works when the receiving device (smartphone) is in a non-shielding housing, such as the Divevolk Seatouch 4 Max Plus
- Another metal housing would block the signal
Close-up view of Sealink components,SeaTouch 4 Max Housing and connection details
Seatouch 4 Max Plus: From Smartphone Housing to Smart Monitor
The Seatouch 4 Max Plus is actually an affordable, full-featured universal underwater housing for many smartphone models that allows touchscreen operation even underwater – without mechanical buttons or levers. The touchscreen works even with neoprene gloves (notably only in water; on land, no gloves should be worn).
In practice, it’s already being used by many divers for underwater photography with smartphones. With Sealink, the housing becomes a smart control station for high-quality camera systems.
Smart Control Features:
- Instead of being dependent on the small camera display, the connection to the app allows the live image to be displayed on the large smartphone display
- Includes touch focus, aperture selection, and video start
- With the right app (e.g., Monitor+; currently only for certain Sony cameras), focus peaking, zebra warning, and false-color images can assist photographers and videographers
- Particularly interesting for macro photography with the large monitor and numerous functions operated by finger touch
Smartphone app interface showing camera control options
Real-World Testing in Cold Water
In two test dives of 35 minutes each at water temperatures between 8 and 12 degrees Celsius, the system proved its practical value.
Setup Process:
- Setup took just under 10 minutes after removing the camera viewfinder
- A ball head for mounting the Sealink module would have been helpful but is unfortunately not included
- The connection between camera and smartphone should be activated before entering the water “ then it remains stable
Performance Results:
- With a Sony A7III and the older “Imaging Edge Mobile” app, the connection was unstable even on land, limited and not really usable (this is due to Sony’s poor “Imaging Edge” app, not the Divevolk product)
- Different story with the Sony A7IV and the new “Creators’ App”: WLAN connection worked reliably after brief setup, touch focus was possible underwater, and live image remained stable
- Canon cameras offer comparable app functions
Important Notes:
- The WLAN connection works “ but only as well as the camera app and manufacturer allow
- Sealink itself is not the weak point, but rather the digital foundation
- Expect significant power consumption from the camera as WLAN transmission drains battery considerably
- The “Seatouch & Sealink” combination creates significant negative buoyancy, requiring buoyancy compensators for balanced trim
Real-world testing setup and underwater configuration
Pricing and Setup
Complete System Pricing:
- Seatouch housing: Euro 249
- Mounting bracket: Euro 59
- Sealink cable with screws: Euro 229
- Prices subject to change
Final Verdict
The Divevolk Seatouch 4 Max Plus gains a new dimension with Sealink. Anyone with a modern system camera with a well-developed app can transform the affordable smartphone housing into a full-fledged control center for underwater photo and video recording.
Advantages:
- Revolutionary passive WLAN technology requiring no power
- Transforms affordable smartphone housing into professional camera monitor
- Large touchscreen control for precise camera operation
- Cost-effective alternative to high-end professional monitors (1/10th the price)
Requirements:
- Compatible camera that supports the functionality
- Quality camera app (manufacturer-dependent)
- Proper setup and careful cable handling
Limitations:
- Won’t replace high-end professional monitors like SmallHD screens or Atomos displays
- Highly dependent on camera manufacturer’s app quality
- Limited range requiring close proximity
- Additional buoyancy compensation needed
While it may not replace professional-grade equipment entirely, this innovative Swiss-reviewed system offers an accessible entry point into advanced underwater photography control at a fraction of traditional costs.
Review source: NEREUS Magazine, Official Publication of the Swiss Underwater Sports Association (SUSV)
Published for divevolkdiving.com
