A 49-year-old US female tourist was killed by a tiger shark this week while diving off a Costa Rican island in the Pacific Ocean, the government and local media reported.
The attack also badly injured the 26-year-old male Costa Rican diving guide leading the group that included the American woman.
The shark savaged the two on Thursday as they were surfacing after a dive off Coco Island, a pristine national park located 500 kilometers (300 miles) off the Costa Rican mainland, the environment ministry said in a statement.
It stressed the attack was "an isolated incident" and the first one of such seriousness recorded for the island.
According to the Costa Rican newspaper La Nacion, the guide noticed the shark approaching his group underwater and tried to scare it away.
But as they surfaced, the shark went for the American woman, tearing at her legs.
The guide, too, suffered leg injuries.
Park rangers came to assist, as did doctors who happened to be diving in the area and who declared the woman dead.
The injured guide was taken to a hospital, where he was in stable condition and conscious. He told La Nacion he believed the shark was a female.
Tiger sharks, which have dark stripes on their body when young, are predators often found around Pacific islands. Unlike many other species of shark, they can be aggressive and account for a large proportion of reported attacks on humans.
Costa Rica, a small Central American nation that boasts both Caribbean and Pacific coastlines, relies strongly on its tourism industry, especially visitors from the nearby United States.