The 36-year-old had been deep-sea diving in Anse Lazio in the archipelago’s Praslin isle on Monday, police spokesman Jean Toussaint told AFP.
“Other tourists on the beach tried to help him, but he died as his injuries were serious,” Toussaint said, adding: “The injuries looked like a shark bite.”
An autopsy was to be conducted Tuesday to determine the exact cause of death, which some officials said could have been as a result of being cut by a boat propeller.
Shark attacks are rare in the idyllic Indian Ocean archipelago.
“I have been diving for the last 40 years and I have never encountered any problems. Sharks are actually very rare because they are hunted for their meat and fins,” said Michel Gardette, a development official in Praslin.
“Seychelles is one of the safest countries for diving,” he added.
The 115-island Indian Ocean archipelago is a popular top-end tourist destination, with some villa accommodation costing as much as 10,000 euros per night.