The Seychelles News Agency has reported that a 45-year-old French tourist was in the water at 7pm off the coast of Praslin, an island of Seychelles, when it happened.
Her arm was "severely injured" in the attack and the woman was flown to a Seychelles hospital by plane.
"She underwent an operation last night and her vital prognosis is not in danger," Dominique Mas, ambassador of France to Seychelles, told the local press.
The news agency also said The Seychelles Maritime Safety Administration is investigating the incident.
