COCOS ISLAND (Costa Rica)- The pristine waters of Cocos Island, 340 miles off the Pacific coast of Costa Rica, saw their first ever shark attack when a 49-year old diver from the US was killed by a tiger shark this week.

The woman, identified as a director at a New York City private equity firm, died after severe bites on both of her legs. The culprit was a female tiger shark.

The woman was ascending to the surface after a dive at the Manuelita dive site when her diving guide noticed the shark. He tried to scare the shark off, but it was too late.

A boater at the surface helped repel the shark as it also attacked the diving instructor, which sustained a bite on one of his legs, but survived. A team of doctors on site treated both the guide as the woman, the Costa Rican Ministry of Environment and Energy said.

Tiger sharks

tigerhookedTiger sharks had not been in the area for about 30 years and returned about a decade ago, local newspaper La Nación reported. According to officials at the Cocos Marine Conservation Area, the attack was an isolated one. In 2012, researchers visiting the island tagged five tiger sharks — two males and three females. The females were the longest, measuring at more than 13 feet. The sharks are most active at the diving sites in the afternoon and early morning hours, but had not presented a threat until Thursday, the Ministry of Environment and Energy said.

Cocos Island National Park, designated a World Heritage Site by UNESCO in 1997, is the only island in the tropical eastern Pacific with a tropical rainforest. The remote island is world famous for its diving, during which tourists can spot rays, tuna, dolphins, and about 14 species of sharks, including the whale shark and hammerhead shark, the Ministry of Environment and Energy said.

Since 1900 Costa Rica has seen 10 previous shark attacks, according to Shark Attack Data. The last one was in 2011, when a 15-year old boy was killed in an unprovoked attack while surfing off Playa Grande, in Guanacaste.