Magpie Morwong

Testing a Shark Shield while snorkeling at Marino

February 28, 2004|Posted in: Dive Reports, Equipment

Having used a scuba-model Shark Shield for many years, I recently had the privilege of testing the new snorkeling version which Mike Wescombe-Down of the Coastal Waters Dive Club kindly loaned me in readiness for the West Coast Blue Groper Survey (See next Newsletter?).

I never actually used it on that trip as I only snorkeled in ‘safe’ inshore areas such as gutters, channels and pools largely protected from the open sea, and when photographing on SCUBA in open water naturally I used my trusty SCUBA model.

So when my son Nick and I popped in off the rocks at Marino for a refreshing dip on Boxing Day at the invitation of new MLSSA member Warwick Noble I thought, ‘here’s my chance.’

Warwick and his partner Monika showed Nick, myself and two other mates of Warwick’s a nice little ledge which which is one of his Dicathais orbita study sites.

Although the viz was only average at about 4 metres, we saw plenty of life, including lots of mainly female blue swimmer crabs, red bait crabs, a wobbegong, a school of big spotted whiting as well as a school of salmon-trout, and many of the ‘usual’ inshore reef fish such as zebrafish, bullseyes, sweep, moonlighters, drummer, sixspine leatherjackets, smooth toadfish, magpie perch (for which I now prefer the term magpie morwong) and dusky morwongs.

Dolphins were also about but we didn’t sight them while we were in the water.

The shield was a breeze to use. So simple as to be virtually idiot-proof, it consists of a lightweight unit incorporating a rechargeable 2 hour battery, well protected in a sleek form-fitting neoprene pouch which can be quickly placed over either lower leg (I use my right leg) and is secured by broad velcro straps.

The flexible ‘tail’, incorporating both polarities of electrodes, on first inspection is awfully long, at about 2 metres, but only the extreme ends contain the electrodes, with the remainder of the black mesh tube (which looks like ‘open weave’ nylon rope) merely serving the purpose of maintaining a reasonable distance between the poles. This is necessary to ensure an adequate radius of protective electromagnetic field (approx. 2 metres) to deter ‘big bities’!

This ‘tail’ is permanently connected to the lower front aspect of the pouched unit and is simply allowed to trail along in the water behind the snorkeler. Although not essential, one can pass it through a little loop in the middle of one’s fin (I find the cable tie through a 5mm hole drilled in the fin is effective), to give extra confidence that it will always trail behind and below one’s fins rather than perhaps ‘washing’ back towards the user. This could feasibly happen (though unlikely, and I have not explained this) if one was stationary in the water, eg holding an anchor line or rock outcrop with one hand with tidal current or surge coming from behind.

As with all such devices, if one accidentally touches either electrode while the device is switched on you will get an unpleasant shock, which however carries very low risk of serious harm.

The sliding on-off switch is easy to feel and operate with one finger or thumb, but the green ‘on’ light, which also confirms adequate battery charge, is less easy to see as its window in the neoprene pouch is rather small. So once the unit is in place on one’s leg one needs to be a bit of a contortionist in the water to view the green light. But as the unit is intended to be turned on immediately upon entering the water and left on until one exits, this ‘one-off’ check is not a great imposition. Indeed, in normal use one checks the unit is functional before entering the water, by briefly turning it on to display the green light even before attaching it to ones leg.

The trailing ‘aerial’ despite its length making it seem high risk for entanglement amongst rocks and algae, gave me no trouble at all, even swimming around in white-water surge over rocky bottom in less than 1 metre depth during entry and exit. And this despite the fact that it has slight negative buoyancy so that it hangs limply down towards the seafloor once one gets to deeper water. (Both electrodes need to be submerged to provide a reliable deterrent field.)

The unit is so light and compact that I can honestly say that I was hardly aware I was wearing it, even when I deliberately ‘crawled’ along the bottom amongst seagrass and low reef to see if I could fault it. Also while doing this I only received a single weak jolt:- I guess it must have ‘shorted out’ for a split second when both electrodes simultaneously contacted the sand or rocks. This would happen rarely if at all during normal usage.

It was indeed nice to trial what is clearly a well designed and highly functional shark-deterrent device in such pleasant conditions. And only days later I eventually observed that the same device was routinely being hung off the back of the charter dive boat while Jenni and I dived the Hobart – very interesting!

[Conflict of interest – none declared]

David is a long-serving member of the Marine Life Society of South Australia. He has dived and snorkeled in South Australian waters for around five decades and has a particular interest in bony fishes. David has made the greatest single contribution to the society’s Photo Index of local marine species.

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