Stealth Diving with HECS: how to be invisible to fish

Who hasn’t thought about being invisible at some time in their life. As an underwater cameraman being ‘invisible’ or more accurately ‘undetectable’ would be awesome. Could a HECS suit system help me get up close to all sorts of marine creatures to film their natural, undisturbed behaviour.

To go undetected underwater by marine life possessing ‘super senses’ we would need to be more than just invisible though, we would also need to mask all the other sensory signals we give off… sound, smell, vibration and even electrical signals.

How important each of these senses are in triggering a flight reaction depends on the species, but if you want to get close to an animal it is common sense to try and tick off as many of those ‘sensory boxes’ as possible, so when I heard about a new ‘underwater stealth technology’ known as ‘HECS’ that blocks a diver’s electrical signals I was keen to find out more!

HECS and how it works:

After meeting HECS developer, Warren Bird, I discovered that HECS is a conductive carbon-fibre mesh woven into a wetsuit, providing a Faraday cage around the diver’s body and blocking the electrical signals given off by muscle activity.  So what is a Faraday cage? …And how important is electrical stimulus to marine life? A Faraday cage is a conductive grid enclosure which blocks electrical fields by channelling the electricity throughout the grid, much like a microwave oven door, and the grid in the HECS suit is the specific size necessary to block human electrical signals. Many marine species are able to detect the electrical signals given off by muscle activity and to some species it is an important sensory input for detecting predators or prey and divers!

Sharks in particular are very sensitive to electrical stimulus, but some other fish species also use electroreception, as do stingrays, salamanders, river dolphins and surprisingly even Duck-billed platypus! Just how many fish species have some level of electro-receptive ability is still being researched, but indications are that it is far more than was thought, and with water being a great conductor it makes good sense for aquatic animals to include electroreception in their sensory arsenal! Warren was really interested in whether HECS would help me get closer to marine life, so with a prototype HECS Neptune wetsuit to test I spent the next few months diving filming and evaluating!

Quantifying how close you get to a wild creature and what has allowed you to do so is not easily measurable as there are many factors in every encounter that can have a positive or negative effect on your success. However I did seem to be getting closer to the subjects I was trying to film when wearing the HECS Neptune wetsuit, and interestingly they appeared to be less bothered by my presence.

Swapping back and forth between the HECS Neptune suit and my regular wetsuit and trying to film the same species each time gave me something to compare to, and while not a perfect scientific test, the contrast in how close I could approach before seeing a shift in behaviour when wearing the HECS suit was consistent enough to convince me it was making a difference.

So is it worthwhile? I think so. ‘Stealth diving’ is a cumulative thing…trying to tick off those boxes to reduce your underwater footprint as much as possible; - moving and breathing slowly, breaking up your outline, and using whatever means you can to be viewed as something non-threatening rather than being seen as a potential predator.
The masking effect of the HECS wetsuit effectively removes another one of those sensory signals from the stealth equation that would be impossible to mask any other way. Fish aren’t super smart their behaviour is largely dictated by sensory input, so the less input they get the less reason there is for them to flee or change their behaviour.

Super Stealth

If you really want to stack the odds in your favour though, combine the HECS Neptune wetsuit with a closed circuit rebreather! My most successful ‘stealth dives’ from a filming perspective have been when wearing HECS while using my Poseidon rebreather – eliminating the sound and visual impact of open circuit bubble clouds AND the electrical signals from muscle activity. The difference in fish behaviour then is clear to see; they just aren’t bothered by your presence.

Of course rebreathers have many other benefits in addition to quiet diving, like optimising your gas mix for whatever depth you are at and allowing for super long dive times. I have been interested in the filming potential of rebreathers for years but was a bit hesitant about the level of technical knowledge necessary to constantly be calculating and making manual adjustments during a dive, a major distraction to filming. However with the introduction of the Poseidon CCR and its level of automation, redundancy and safety features, I was a convert.

The Poseidon CCR’s are compact, comfortable, easy to set up and have huge benefits over Scuba when it comes to bottom time and ‘stealth’. They have clear instrumentation as well as a HUD (heads up display), vibrating mouthpiece warning system, and simple one touch bailout system that switches straight to air. Being modular it is easy to extend the Poseidon’s capability to encompass Trimix and increase your depth range from 40M up to 100M by upgrading the smart battery, (after doing the necessary training of course!)

The two technologies – HECS and CCR [closed circuit rebreathers] complement each other perfectly when it comes to approaching shy marine creatures, – a benefit not just to scientists, photographers and film makers but to any diver wanting to get closer to marine life.

What these technologies also point out though, is just how poor our own underwater senses and abilities are when compared to those of aquatic life; stealthy we are not without help anyway!