A shark bit off the leg of a young US woman while snorkeling on a Caribbean boat excursion, say reports

• A shark attacked a 22-year-old woman while she was snorkeling in Turks and Caicos.
• A hotel employee who witnessed the incident said the victim had her leg bitten off, police said.

A shark bit off the leg of a 22-year-old woman from Connecticut in Turks and Caicos, according to a witness, authorities said.

The woman was snorkeling with a friend in the waters outside Blue Haven Resort when they were attacked by the shark, according to the Royal Turks and Caicos Islands Police Force.

An employee of the resort called for an ambulance and indicated that the victim had her leg bitten off, the police said

The woman remains in serious condition in hospital, the police statement said.

A resort spokesperson told NBC News that the woman was not a guest and the incident is not linked to the resort or the Leeward Marina.

"Our understanding is that she was the guest of another resort and the client of a boat excursion company, neither of which we are affiliated with nor located near," spokesperson Stephanie Mack said.

Shark attacks on humans are extremely rare. There were just 57 unprovoked shark bites worldwide last year, of which five were fatal, according to the University of Florida's International Shark Attack File.

Sharks have been known to attack humans when confused or curious, such as when they see a human splashing in the water. Research has also suggested that sharks might attack when they mistake humans for prey, such as seals and sea lions,

Some scientists have often said that there is no real evidence that sharks bite humans because they want to eat them or see them as food, and attacks are bitten by accident while sharks are hunting marine prey at high speed.