I’ve been taking an increasing interest in more exotic and technical diving and that’s led me to complete my advanced nitrox / decompression procedures class and schedule one for technical sidemount. While I’m still not ready to take the plunge, but I’m fascinated by cave and wreck diving, and I’m sure its only a matter of time before I get there.
While idly looking through catalogs of tech diving gear, I realized that diving helmets are unjustifiably expensive. Diving helmets have two jobs: protect the diver’s head from knocks, and act as a stable mounting point for lights and cameras. Both are easily achieved by airsoft helmets, but where they differ from helmets is that they have to be (close to) neutrally buoyant and not have any air- or water-trapping foam.
None of these are technically challenging to achieve, so I was surprised to see suspiciously generic looking helmets with eye-watering price tags. Running a reverse image search on one of the dive helmets, I found this airsoft helmet for under US$30. Score!
Most airsoft helmets are durable against repeated contact with rock surfaces. Low-profile mounting rails and attachment points allow secure placement of lights and cameras while minimizing the risk of snagging, and the adjustable nylon straps ensure a good fit that stays put when entering and leaving the water. The helmet I found had holes in the crown to avoid trapping air and removable foam padding, making it an ideal starting point for my diving helmet.
Parts
As my dive instructor assured me, the cat ears are the single most important item for wreck diving. Here are the other key parts of the helmet:
Forward Lights
The side rails are almost (but not quite) picatinny, as is traditional for airsoft or milsim helmets. I chose a Wurkkos DL07 as the dive light for its small size, good brightness in flood mode, and a UV mode that helps light up coral. Getting the light clips right took a little effort, particularly with the clamping mechanism, but eventually worked well.
There are two independent retention mechanisms holding the light to the mount: the thin curved wall clamping the barrel, and a 1/4-20 knurled knob. The clamp is strong enough to hold the light onto the helmet on its own through a giant stride entry (into my local swimming pool), and is easy to repeatedly clip and unclip without removing the helmet. The use of a knurled knob (instead of a SHCS bolt) for secondary retention allows for tool-free disassembly underwater.
You can download it here, and the design files.
Rear light
For easy identification, we include a small green strobe at the rear which is velcroed on. After some testing, it would have been much more visible on my tank strap instead of my helmet.
Padding
The original padding was somehow very buoyant and would soak up water readily, rendering it unsuitable for underwater use. I replaced it with padding 3D-printed in TPU.
The TPU used was Biqu Morphlex 75A, printed in a 10% gyroid infill without side walls and with striped top walls. Gyroid forms a regular open-cell structure that allows water to flow in and out readily, and the infill size is chosen so that water drains easily. You can download the Fusion files for the top and side.
Weight and Buoyancy
In its final configuration, I will be diving it with only one of the two lights and without the cat ears. In that configuration, it weighs about 900g in air, and about 400g under water. This weight is tolerable through a 30-minute test, but for longer dives, I may add shaped buoyancy floats to the inside of the helmet to balance it. These would be made of either EVA sponge, some kind of closed-cell UHMW foam, or foamed ASA.