It has traditionally been believed that sharks are repelled by the smell of a dead shark; however, modern research has had mixed results. The Pardachirus marmoratus fish (finless sole, Red Sea Moses sole) repels sharks through its secretions.
The market offers five main types of shark deterrents: magnetic repellents, electric repellents, sound repellents, semiochemical repellents, and visual repellents. They reach the consumer market in the form of surf leashes, rubber bands, spray cans, and wetsuits.
Sharks appear to dislike the noise of the bubbles scuba divers create as they breathe underwater. One researcher also found that playing the AD/DC song "You Shook Me All Night Long" did not repel sharks, but did seem to calm them and make them less aggressive, perhaps because they were curious about the sound.
Magnets repel sharks, studies show, by interfering with their ability to sense electrical fields. A recent study shows that magnets placed on the nets can repel sharks and rays from entering the trap.
FACT: Sharks know the difference between fish and human blood and, while they can smell our blood, it is not a scent they associate with food. Scientific experiments have repeatedly shown that sharks have no interest in human blood.
No reaction. From a scientific standpoint, Esbaugh says that it's “definitely not true” that sharks are attracted to urine, and he assumes the rumor got started because many animals use scent to track their prey. But he says this doesn't hold up because humans aren't the most common meal for sharks. Fish are.
But sharks don't have the capacity to smell fear. That doesn't mean that a shark isn't impressive with its ability to detect prey from vast distances using its sense of smell, however. Fear is a complex emotion and a shark's olfactory system isn't sufficiently equipped to detect it.
Sharks are often viewed as one of the ocean's top apex predators, but despite this rather prestigious classification, there's one marine animal that most sharks prefer to avoid crossing paths with entirely: the bottlenose dolphin.
Alternatively, divers and swimmers can probably reduce the chance of an interaction with a shark by avoiding bright and highly contrasting swimwear or dive gear. We personally prefer to use dark blue or black fins, mask, tank, and wetsuit while diving.
In fact, sharks can see extremely well in dark lighted areas, have fantastic night vision, and can see colors. Avoid wearing bright colors, such as oranges and yellows, in the water, as sharks can indeed see them.
Since sharks see contrast colors, anything that is very bright against lighter or darker skin can look like a bait fish to a shark. For this reason, he suggests swimmers avoid wearing yellow, white, or even bathing suits with contrasting colors, like black and white.
Repress the urge to scream. Screaming will not deter the shark much and may provoke it further.
Be aware that activity which might imitate a prey animal in distress — such as splashing, slapping the water, and screaming — might attract sharks.
Overfishing. Overfishing is the biggest threat to sharks: more than 100 million shark are killed every year, with a large number of them being caught for their fins.
Avoid thrashing around and looking like prey. If the shark makes contact, discourage it by hitting its nose, eyes, and gills. And if the shark bites you, seek medical help right away.
Bright is best
In open water, bright, neon colors, including orange, yellow, and lime green, fared best.
Refrain from excess splashing, as this may draw a shark's attention. Do not allow pets in the water: their erratic movements may draw a shark's attention. Be careful when occupying the area between sandbars or near steep drop-offs-these are favorite hangouts for sharks. Swim only in areas tended by lifeguards.
Magnetically sensitive sharks don't like samarium, neodymium, and praseodymium, according to a report by BBC on a company that is experimenting with rare earth elements to protect swimmers from getting bit.
Sharks prefer to avoid dolphins. Dolphins are mammals that live in pods and are very clever. They know how to protect themselves. When they see an aggressive shark, they immediately attack it with the whole pod.
The most common form of defense is speed; dolphins are incredibly fast swimmers and can outrun most species of shark, meaning they are often able to evade attack by simply outswimming their opponent.
As the shark swims around you, keep your head on a swivel and try to maintain eye contact. “Sharks are ambush predators,” Peirce explained. “If you're turning around and facing it the whole time while it circles you, it's not going to be half as comfortable as if it's able to sneak up from behind.”
Sharks are simply not attuned to sniffing out human blood because humans are not part of their diet. Most sharks eat other fish so that is what their senses are designed to recognize. In addition, the amount of blood that could be released into the water by a woman swimming while menstruating is very small.
Sharks can smell blood from up to around a quarter of a mile away. When you smell something in the air, it's because scent molecules have dissolved into the wet lining of your nose. Smelling underwater is no different, except that the molecules are already dissolved in the seawater.