ESDs aim to overwhelm a shark's electro-sensory system. They emit electrical pulses (each one does so in a different way) that are supposed to repel the shark. So far, ESDs have been the most effective type of personal shark repellent.
Natural repellents
The Pardachirus marmoratus fish (finless sole, Red Sea Moses sole) repels sharks through its secretions. The best-understood factor is pardaxin, acting as an irritant to the sharks' gills, but other chemicals have been identified as contributing to the repellent effect.
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.”
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.
Sharks will generally hunt at dawn and dusk and at night, but like many predators will feed at any time they come across prey unless they have just eaten and some female sharks like the female Grey Nurse Sharks do not eat at all during mating season.
A recent study, conducted by experts at the University of Miami, found that sharks are swimming closer to the shore than people might realize.
They discovered that certain copper compounds, like copper acetate, when combined with other ingredients, could mimic the odor of a dead shark and drive live sharks away from human beings in the water.
Sharks are apex predators, meaning they sit at the top of the food chain. Sharks help preserve the fragile balance of ecosystems by keeping other populations in check. They keep populations healthy, too, by dining on the sickest and weakest of their prey so that the healthy can thrive.
But, if a shark is near you in the water, stay calm and don't flail your arms. Experts say the best thing to do is to swim slowly and keep eye contact with the shark. They say the only time you should defend yourself is if a shark looks aggressive. In that case hit either its nose, eyes, or its gill openings.
Bump and bite: Bump and bites usually start with the shark circling around you, then they will engage by bumping into you then taking a bite. Usually this is like a hit and run where a shark is motivated by curiosity or sometimes, territorialism.
We personally prefer to use dark blue or black fins, mask, tank, and wetsuit while diving. Make a point of wearing your dive watch under the cuff of your wetsuit, thereby eliminating any chance of light reflection off the face of the watch attracting a shark or barracuda.
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 being in the water during low light hours (dawn or dusk) and at night when many sharks are most active and feeding. Sharks have never been shown to be attracted to the smell of human blood, however, it may still be advisable to stay out of the water if bleeding from an open wound.
So while it's unlikely that sharks can read our minds and know when we're in trouble, they can sense distress in other aquatic animals and respond accordingly. While we may never know for certain if sharks can sense our fear of them, they certainly have that effect on us.
If a shark sees a human splashing in the water, it may try to investigate, leading to an accidental attack. Still, sharks have more to fear from humans than we do of them. Humans hunt sharks for their meat, internal organs, skin, and fins in order to make products such as shark fin soup, lubricants, and leather.
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. Shark-repelling magnets may be the perfect antidote to unwanted shark attention while fishing.
Pinnipeds (seals and sea lions) aren't the only marine mammals that have snacked on a shark. The sperm whale is a marine mammal that is considered an apex predator in certain habitats and it has been recorded as having eaten shark eggs.
If you see a shark near you, just get out of the water. Give them their space and come back and surf later. Chances are that if you see them you're probably safe since they do love a good sneak attack, but just the same, this small preventative measure may keep you surfing for years to come.
Sharks are most attracted to low-frequency, erratic thumping sounds that mimic prey in distress. In the Discovery Channel's Bride of Jaws (2015) documentary, researchers used an underwater speaker playing heavy metal music (low-frequency dominated music) to successfully lure great whites for filming purposes.
Everybody can make their own personal decision, but realizing that sharks can get into water as shallow as five of six feet deep is something that people need to realize.”
1. Great White Shark. Great white sharks are the most aggressive sharks in the world has recorded 333 attacks on humans, with 52 of them being fatal. The inclusion of this particular species probably comes as no surprise since movies, particularly Jaws, and television shows are quick to show their aggression.