Police Lieutenant Visawa Sane-ha, from the Ao Nang police station, said the 42-year-old tourist was identified as Olivier Jannequin.
Lt Visawa said Mr Jannequin was snorkelling with a friend near the beach around midday when the friend started seeing blood in the water.
“The friend suspected that the speedboat propeller had hit Mr Jannequin in the head and body,” Lt Visawa said.
Mr Jannequin’s body remains at Krabi Hospital. Police are investigating the incident.