The shark-repelling electroshock surfboard

If you're that worried about being eaten by a shark you might want to consider staying out of the water and taking up a less dangerous hobby, but an Australian company called SeaChange is showing off a prototype for a surfboard that emits some kind of shark-repelling electrical field (don't ask us how it works or why it doesn't shock also the surfer). 

[Jamaicanbwoydre @ Dec 19th 2005 12:03AM]

Maybe because Sharks have a remarkable gel in their snouts that produces electricity in response to minute temperature changes, enabling the fish to spot heat differences in water that could lead them to prey, the gel lies in long channels, about 10 centimetres (four inches long), beneath the shark's skin, which connect pores on the surface with sensors called ampullae of Lorenzini. These sensors are already known to be highly sensitive to electrical fields generated in the water by the muscles of a wriggling or wounded fish, perhaps even the heartbeat of a swimmer.


So maybe the surfboard would put out an electrical jammer, so to speak that might disrupt or disorient the shark so i would just turn away or get stunned so the surfer could escape. Cool concept.

[Grendel @ Dec 19th 2005 12:03AM]

As stated above sharks have an extremely sensitive system for detecting changes in electrical potential underwater. It's quite likely that voltages required on the surfboard to disrupt this and repell the shark is well below the threshold of humans sensitivity.

[Alex Vaughan @ Dec 19th 2005 12:03AM]

Read Nature, do we?

But sharks tend to fixate on an electrical dipole, such as that created by a fish swimming around. When presented with a dipole, they will fixate on it, and essentially attempt to eat it.

So - this cannot be a simple DC voltage, since that would look like a fish (or at least something interesting).

But: a) How do you make an anti-dipole? Is it just really fast AC currents to act as a jamming device? b) Then again, no-one seems to know why fish make a dipole, so they may have thought of some other way to correct this without making you look like floating sashimi.

[May @ Dec 19th 2005 12:03AM]

This company apparently makes a specialized military version of the shark shield as well as a line of shark-repelling devices you can strap on to your leg (for divers and swimmers)

http://www.sharkshield.com/introset.html

[May @ Dec 19th 2005 12:03AM]

This company apparently makes a specialized military version of the shark shield as well as a line of shark-repelling devices you can strap on to your leg (for divers and swimmers)

http://www.sharkshield.com/introset.html

[Macstibs @ Dec 19th 2005 12:03AM]

Sharks are highly sensitive to current. (Refer to that bit about Lorrenzini) Any current that is more significant than say, a muscle twitch, essentially overloads the shark's nervous system. By strapping a coupla 9volts to your leg, you can create a field that disrupts a sharks nervous system, causing the shark to spasm uncontrollably and seek food elsewhere. It's called aversion therapy... I'm trying to work a system out that'll give the gf a shock if she touches my wallet.

[Mark Kawakami @ Dec 19th 2005 12:03AM]

This might be all right for surfboards, but generally research has shown while electricity can be used to repel sharks who are approaching out of curiosity, a lot of sharks in an excited state can ignore this, because whatever is exciting (typically blood and thrashing movements) override the input from their Ampullae. Now, the good news is that most "attacks", especially from larger sharks, are exploratory in nature, however they explore with their mouths (lacking any other suitable body part). So this should help many of those. The truth is, though fancy electric repellant or not, more people are trampled to death by rhinos each year than eaten by sharks, so swim on.

[C Cummings @ Dec 19th 2005 12:03AM]

They were testing this technology on the Discovery Channel with another one those crazy Australian adventure guys (not Steve Irwin aka Crocodile Hunter). The version on the television show was akin to a "bang stick", but with a sensor on the end that apparently disrupts the electrical field enough to repel the shark. No significant current is actually emitted from the device, which I'm guessing is what is going into these surfboards (especially given the Australian connection). On the show they tested the stick on white tip sharks, which are apparently the most aggresive of all species (according to the host). They sure did seem aggressive - approaching without fear, and without any signs of struggle from the divers. The stick was "poked" at our around the shark's snout and caused an immediate reaction, but obviously would not be a deterrent for more than one or two sharks, nor would it be a long-term deterrent. In other words, given enough time in the water, the sharks eventually came back again.

[Paul von Blerk Natal Sharks Board @ Dec 19th 2005 12:03AM]

The Natal Sharks Board of South Africa Developed this technology and continues to carry out R+D in this field. It entered into an agreement with the Australian company called SeaChange which continues to use the technology but has packaged it in different ways.

[Vincent Borg @ Dec 19th 2005 12:03AM]

I recall watching the Discovery bit...some sharks went into a spasm of about 0.5 per second or less.
I wonder if each pulse was a train of rapid pulses or a single one ??
Also interesting, is the question of the pulse being DC or Alternating polarity.

If sharks are so sensitive to electrical fields, then surely a terminal potential difference of say 30 Volts will be devastating to them. This voltage should be safe to humans.
More than likely, other marine life might find it uncomfortable, but I prefer to keep all my limbs.......Oh and just in case the tree-huggers out there think otherwise and say that its their territory, Well its mine too.
Vincent Borg
Malta