The woman, aged around 20, sustained bite wounds to her leg during the incident which took place as she swam in the sea close to the beach in southwestern l'Etang-Sale.
She received first aid at the scene before being taken to hospital but died later of a cardiac arrest, the local prefecture told AFP.
The attack comes after a 23-year-old man was attacked at almost the same spot last October. He survived but lost his right leg.
Several months earlier in July 2014, a 51-year-old surfer also suffered multiple bites in another attack at Saint-Leu in the southwest of the island, around 200 kilometres east of Madagascar.