Are Whale Sharks Dangerous to Humans? Gentle Giants Explained

Why whale sharks are harmless

The whale shark is the largest fish in the world, with adults commonly 8–12 m (26–39 ft) long, but it is built for a gentle lifestyle. It feeds by straining tiny food from the water through spongy filter pads in its throat, as explained in What do whale sharks eat? It does not hunt large animals and has no reason to see a swimmer as prey.

Its mouth holds more than 300 rows of tiny teeth, but each is only a few millimeters long, and they play no known part in catching food. Whale sharks swim slowly, usually at about 2–5 km/h (1–3 mph), and they tolerate snorkelers and divers well enough that swimming with them has become a major tourist activity in more than a dozen countries.

Whale sharks are not aggressive. When they are crowded, touched or blocked, they typically dive, turn away or change direction rather than react against people. Compared with the real but small risk posed by some predatory sharks, described in How often do sharks attack humans?, the whale shark is about as safe as a large wild animal can be.

The real risks: size, tails and boats

Any animal weighing many tonnes deserves respect. The most likely way to get hurt is to be in the wrong place when a whale shark moves. Its tail fin is tall and powerful, and a sideways sweep can knock a swimmer or diver hard enough to cause bruises or worse. A shark that suddenly turns or dives may also bump a person who is swimming right beside it.

Other risks have nothing to do with the shark. Popular sites can be crowded with boats, and swimmers in the water near moving vessels risk being hit by propellers. Strong currents, choppy water and long swims in the open sea are a challenge for weaker swimmers. Good operators brief swimmers, provide flotation and keep boats well away from people in the water.

Serious injuries are very rare. If anyone is hurt at sea, seek emergency medical help immediately: call 911 in the US, 112 in the EU or 999 in the UK, or alert the boat crew to radio for help.

Could a whale shark swallow a person?

No. This fear comes from the size of the mouth, which can be about 1.5 m (5 ft) wide in a big adult. But the whale shark’s whole feeding system is designed to sieve small food, and it swallows nothing larger than small fish and squid. Videos of divers close to a whale shark’s open mouth sometimes go viral, but the shark is simply feeding or passing by, and it does not treat people as food.

Some people have wondered whether the “great fish” in the story of Jonah could have been a whale shark, but there is no evidence that any whale shark has ever swallowed a person.

How to swim with whale sharks responsibly

Most whale shark sites have codes of conduct, and in many places they are law. At Ningaloo Reef in Western Australia, home to one of the longest-running whale shark tourism programs, the rules have long included:

• Stay at least 3 m (10 ft) from the shark’s head and body and 4 m (13 ft) from its tail.
• No touching or riding the shark, and no blocking its path.
• No flash photography and no motorized underwater scooters.
• No more than 10 swimmers in the water with one shark at a time.

Boats are also controlled. At Ningaloo, a 250 m (820 ft) contact zone around each shark limits how many vessels can approach at once. Other countries have similar rules, and some sites, such as Mexico’s Caribbean coast, allow snorkeling but not scuba diving with whale sharks. Following the rules protects people as well as sharks: keeping clear of the tail is the easiest way to avoid an accidental blow.

Are people a danger to whale sharks?

People are far more dangerous to whale sharks than the other way round. The species is listed as Endangered by the IUCN, after a decline of more than half over about 75 years, caused mainly by fishing, bycatch and ship strikes. Whale sharks feed slowly at the surface, which makes them vulnerable to collisions, and at many tourist sites a large share of the sharks carry propeller scars.

Badly managed tourism adds pressure. At Oslob in the Philippines, boatmen have hand-fed whale sharks since 2011 to guarantee sightings, and scientists have raised concerns that this changes the sharks’ natural behavior and keeps them close to boats. Touching, chasing and crowding can also disturb sharks and interrupt their feeding.

When choosing a tour, look for operators that follow the local code of conduct, limit swimmer numbers and do not feed the sharks.

Where people swim with whale sharks

Whale sharks gather in predictable places when food is plentiful, which is why tourism is concentrated at a few sites:

Other gentle giants are just as safe to watch from a respectful distance, including the basking sharks of British and Irish waters, covered in Are basking sharks dangerous?, and the manta rays of tropical reefs, covered in Are manta rays dangerous?