Shark repellents are essentially any method of driving away sharks from an area or a person. Interest in shark repellents go back a long time where scientist and inventors constantly trying to create different kinds of repellents ever since the growing fear of shark attacks spread  more through cinema and media coverage of isolated incidents than by actual threats. It was reported that in the year 2000 a total of 79 incidents of shark attacks were recorded worldwide, out of which only 11 were fatal, and in 2006 a total of 61 attacks worldwide were recorded.

Still the interest in shark repellents is ever growing, with various forms being marketed to local governments to install in beaches, or to fish farmers to protect their fish, and to researchers, surfers and scuba divers.

The main forms of shark repellent technologies used today are in the form of Magnetic Repellents, Electropositive shark repellents and Semiochemical.

Electropositive Shark Repellents
These use an electropositive metal which when immersed in an electrolyte generates a voltage which overwhelms with ampullary or electro-sensory organ in sharks, producing a repellent action. This ampullary organ isn’t found in other bony fish other than sharks and rays making its effectiveness shark-specific. The whole process is electrochemical where the chemical electrolyte reacts with the metal alloy, and does not require an external power supply. However is said that electropositive shark repellents are not 100% effective, and are only useful when a shark is using its electro sensory organs, and will not help when a shark is in a feeding frenzy. Hence the usage of these repellents is limited to fisheries or fish farms where they can keep predators away from stocks. Also electrochemical metals have a very limited lifespan and need to be changed constantly requiring constant maintenance and upkeep costs.

Magnetic Shark Repellants
Magnetic repellents as the name suggests use permanent magnets to exploit the shark’s electroreceptor’s located in its nose known as  Ampullae of Lorenzini, which similar to the electropositive method, impacts only sharks and rays which possess this organ. Several species of sharks have demonstrated the ability to sense magnetic fields and magnets are said to over-stimulate the electro-sensory receptors thereby effectively repelling them. However once again if the sharks sense of smell is overpowering the electro-sensors, or if the magnet is not in sufficient range to impact the sharks sensors, the shark may still attack. Research is still being conducted on the effectiveness of this method. The advantage of using magnets is that they need not be large and bulky, so not need to be renewed and can be worn by surfers and divers as necklaces/anklets or bracelets. Magnets are also being purported  to be the answer to shark conservation by having long line fisherman attach a magnet to each long line just above the hook to prevent sharks being caught in them.

Semiochemical Shark Repellents
Semiochemical repellents consist of a chemical mixture that sends out a signal to the shark which is derived from one of its natural responses. Semiochemicals  encompass pheromones, allomones, kairomones, attractants and repellents. Certain extractions have the ability to trigger a flight reaction in sharks making them the most effective form of repellent. However identifying and isolating the correct cue mixture is no easy task, but some researchers have claimed to find the right formula. Semiochemical repellents are currently sold in the form of surface aerosol cans and liquid canisters for fisherman and researchers and most liquid/aerosol shark repellents sold in the market today are semiochemical repellents.

All repellents to date are only partially effective and no form of shark repellent is a 100% effective against sharks. The effectiveness of each of the above techniques varies from one shark species to the next. Using a shark repellent is not a license to go swim with sharks, nor is it a substitute for common sense which is your best defense against a shark attack.

photos by: dorkula (Carrie Sloan), 126 Club

With close to 450 different species of Sharks that inhabit the oceans, sooner or later a Scuba diver is bound to spot one. To some of us spotting a shark on a dive is a great thrill and to others our worst nightmare. We have compiled a list of some of the more common and interesting shark species to help better identify these intimidating yet magnificent creatures.

Black Tip Reef Shark

One of the more common sightings on a reef dive is the Black-Tip Reef Shark which are found in the shallow coral reefs of tropical waters primarily in the indo-pacific. With a brownish skin color, the tips of the shark’s pectoral fin and dorsal fins are black, with a white underside. It has been recorded at up to 2 m (6.5 ft) in length and over 99 lbs (45 kg) in weight. Black tip reef sharks feed mainly on reef fish and are not known to attack divers.

White Tip Reef Shark

Also a frequent sighted shark, Whitetip reef shark are also found along the indo-pacific coral reefs and sometimes as far east as south Africa and Central America.  The Whitetip shark grows up to 1.6m (5.2ft) in length and is easily recognizable by its white-tipped dorsal and caudal fins. Living off a diet of fish, crustaceans and octopus, this species hunts mainly at night and are seldom aggressive towards humans.

Nurse Sharks

Are found in the shallow tropical and sub tropical waters of the western Atlantic and eastern Pacific regions. Nurse Sharks can grow to a length of 4.3 meters (14ft) and is recognizable by its distinctive mouth which is far ahead of its eyes and made for bottom-feeding. Nocturnal by nature these sharks feed on crustaceans, mollusks stingrays and other fish.  Nurse sharks typically attack humans only if directly threatened.

Whale shark

These colossal creatures grow to a length of 20m and weigh up to 12,000 Kg feeding off zooplankton, squid and small fish. Found in all temperate and tropical regions, whale sharks  are instantly recognizable by its distinct spotted and striped body and wide mouth. Whale sharks are gentle giants and are very popular with divers that enjoy observing and swimming alongside these creatures while feeding. This species, despite its size, does not pose any significant danger to humans.

Blue Shark

All sharks swim very fast, but the blue shark is the fastest. These slender looking blue-skinned sharks can grow up to 12 feet long (4 meters). Inhabiting mainly the tropical and temperate waters of the ocean, the Blue shark is highly migratory. Its diet is mainly composed of squid and small bony fishes. The blue shark is considered to be one of the more dangerous sharks. It has been known to attack humans, which makes it one of species of shark that people most fear, however according to Wikipedia only 4 recorded Blue Shark fatalities have been recorded as of 2008.

Hammerhead Sharks

The most unique species of shark and also one of the more recognizable ones is the Hammerhead shark. Growing to a length of up to 6 m (20ft),it is known for its flat hammer shaped snout. Hammerheads inhabit temperate waters across the world ranging from southern Canada to New Zealand. Known to possess especially well developed electro-receptors  for hunting, hammerheads feed on a variety of fish and bottom dwelling creatures. There have been reported cases where Hammerhead sharks have attacked humans which are why they are feared.

Bull Sharks

Often confused with the great white shark, the bull shark is amongst the top three most dangerous sharks roaming in our oceans. The bull shark has a short, wide, rounded snout and plumper bodies.  Bull sharks are known for their aggressive behavior and the fact that they can live in both freshwater and saltwater. They can live in rivers, estuaries and some lakes in Central America. In fact, some have been found as far as 3000 km up the Amazon and Mississippi rivers. Bull Sharks feed on a wide variety of creatures including turtles, dolphins, seabirds and even other sharks.

Sand Tiger Sharks

Sand Tiger Sharks are also known as Grey nurse sharks are rather slow moving sharks and not aggressive to humans unless provoked. It grows to a length of 3.2 m (about 10.5 ft) and is identifiable by  its grey back and white underside. Found in the coastal waters of tropical and temperate regions, Sand Tiger sharks feed primarily on bony fishes including mackerels, other sharks and rays, squids, crabs and lobsters.

Tiger Sharks

Tiger sharks are perhaps most well known for their aggressive natures and bad reputation as a threat to humans. Second to the Great White, the Tiger Shark is responsible for the second highest number of fatalities related to shark attacks. Growing to a length of 5 meters and reaching a weight of almost 700kg tiger sharks will eat almost anything. They have been known to feed on whales, squid, fish, and turtles and even seabirds.

Great White Sharks

The big daddy of all sharks and also the most feared predator of the seas, the Great White like the Tiger Shark will feed on anything. Averaging about 4 to 6 m (13 to 20 ft) Great Whites diet mainly comprises of seals, dolphins, whale carcasses, seabirds, turtles, squids and other sharks. The Great White Shark is found near the coasts of California, Australia and South Africa. Known to be responsible for almost 10 human fatalities a year, diving with Great Whites must be performed only with highly experienced divers and from the safety of a shark cage. (Also Read: Overcoming The ‘Jaws’ Factor When You Dive)

Photos by:WIlly Volk, StormyDog, richard ling, bryan scott photography, jon hanson, pterantula, Nemo’s great uncle, Thespis377, g-na

For the Best in Scuba Gear and Equipment right from Scuba regulators, Wetsuits,  Buoyancy Compensators, Scuba Accessories, underwater camera housings and more visit LeisurePro.com- The Diver’s Emporium

Many people are unsure about Scuba Diving and claim with certainty that they would never try it. Ask them why? and one of the most common replies is ‘Are you kidding? I’ve seen the movie Jaws!’. So is this fear of sharks and Scuba diving justified?

(*Photo by SF Brit on flickr)

Well, we’d be lying if we said that the chances of seeing and encountering a shark was low or even non existent. Let’s face it, you dive in open waters and as the biggest predators in the ocean, there are over 400 different species of sharks. However, hundreds of thousands of divers encounter them on dives across the world and that’s not counting the daredevil kind who specifically go shark diving wanting to cross it off their ‘list of things to do before I die’ and they don’t become shark bait.

Contrary to popular belief, Jaws and the endless shark attack programs shown on TV, there have been very few shark attacks on Scuba divers.  Let’s just say your chances of getting hit by lightning, dying of a wasp, bee or snake bite are a lot more than becoming a shark’s supper. In the United States the annual risk of death from lightning is 30 times greater than that from shark attack. (*Photo by manoellemos on flickr)

If you think about it logically, Sharks just like most animals are weary of foreign objects (read as humans in the ocean!). Look at it from a shark’s point of view- if you came across a noisy bubble blowing, large strange shaped  creature carrying Scuba gear and equipment on their backs that often flashes bright lights (with dive flashlights or underwater cameras) and not to mention in groups or at least more than one, would you stick around to figure whether they would harm you? If you’re still thinking, the answer is No.

Worldwide there have been probably 70-100 shark attacks annually resulting in about 5-15 deaths as compared to the millions of dives conducted each each. Of these the Scuba diving related shark attack percentage is very low. The majority of this unfortunate incidents occurred to surfers, swimmers, skin divers, kayakers while swimming or surfing in near shore waters. In most instances, these probably are cases of mistaken identity that occur under conditions of poor water visibility and not an intentional to feed on the human. The victim seldom sees its attacker and the shark does not return after inflicting a single bite or slash wound as it soon realizes that it isn’t it’s usual prey.

As bad as a Shark taking a nip at you may sound and with no intention of downplaying the severity of the situation, the shark attack trauma is less common than such beach-related injuries as spinal damage, dehydration, jellyfish and stingray stings and sunburn.

A few stats on your odds of being attacked according to the Florida Museum of Natural History based on data from 68 ocean lifeguard agencies within jurisdiction is
Drowning and other beach-related fatalities - 1 in 2 million
Drowning fatalities -  1 in 3.5 million
Shark attacks -  1 in 11.5 million
Shark attack fatalities - 0 in 264.1 million
(*Photo by c.lathe on flickr)

At first many divers find the thought of sharks quite disturbing mostly cause they tend to have a certain presence that you can’t quite trust. But if you do get the pleasure (yes, it is exhilarating to be in the presence of such a creature) of seeing one, you will find that they tend to be more afraid of you than you of them with the exception of a few types (namely- the Great White Shark, Tiger Sharks and Bull Sharks). Sharks are definitely not the evil monsters that you see on TV. They truly are very misunderstood.

If this is still the only unnerving fear you have of Scuba diving, the best and only way of overcoming it is facing it head on. Only by experience will you get over your fears and it won’t take you long to wish you spot a harmless shark on a dive.

For those divers who still get the jitters when they hear the word Shark, look out for our Tips on How to React in the presence of a Shark. (*Photo by StormyDog on flickr)