SAN JUAN, Puerto Rico (AP) — A shark estimated at 6 feet (1.8 meters) long bit a US tourist earlier this week while she swam in a popular bioluminescent bay at night, doctors said yesterday.

The woman, identified as 27-year-old Lydia Strunk faces several months of physical therapy and will remain hospitalised until the weekend, Dr Ernesto Torres said. The victim is a law student in San Diego but is originally from Wendell, Idaho, said Natalia Robles, a friend in Puerto Rico.

The wound is about 10 inches (25 centimeters) long and runs from below her knee to the ankle, said Dr Pablo Rodriguez, trauma director at the Rio Piedras Medical Centre.

“It was like (the shark) tried to tear away,” he said. “She has an imprint of all the shark’s teeth.”

Strunk is expected to make a full recovery but will likely have some nerve damage and limited movement in her right foot, he said. Doctors repaired four tendons that are used for flexing the foot, and it will take up to five months for Strunk’s damaged nerves to grow back, he said.

The shark bite was confirmed by a marine biologist, but he could not identify the type of shark because no teeth were recovered, Torres said.

Strunk has declined to speak to the news media and does not want photos of her injury released, doctors said. Her parents are expected to arrive in the US Caribbean territory Thursday afternoon, doctors said.

Strunk was one of 16 people kayaking late Tuesday in the bioluminescent Mosquito Bay in Vieques, a tiny island just east of Puerto Rico. She jumped into the water with four other people when something hit the leg of the person next to her. Seconds later, Strunk was bitten, doctors said.

“The shark’s mouth basically clamped over her calf,” Rodriguez said.

The shark was likely curious, according to the biologist who analyzed the bite.

The bay attracts hundreds of visitors mesmerized by its glowing waters that are activated when microscopic organisms are disturbed. But its murky waters also serve as a nursery for several species, including tiger, nurse, reef and hammerhead sharks.

The Department of Natural Resources is investigating what company, if any, organized the kayak trip, spokeswoman Ana Maria Ramos said.

People are prohibited from swimming in the bioluminescent waters of Mosquito Bay to protect the ecosystem, and the company could face a penalty of up to US$5,000 or even lose its license, she said.

Despite the regulations, kayak operators often allow visitors to swim there.

The shark bite was reported to the Florida Museum of Natural History, which records such statistics.

Shark attacks are rare in Puerto Rico. Only seven attacks have ever been reported, two of them fatal, with the last death occurring in 1924, according to museum statistics.