The 61-year-old tourist was snorkeling on Maui Friday when the shark attacked him about 200-yards offshore.
Thomas Kennedy suffered cuts on his leg and thigh and was taken to a hospital after being treated by lifeguards. He told a state biologist the shark's head was about two feet wide.
"Based on my estimate of the size of his head, the coloration and the shape, and I'm certainly not an expert, but his guess was it was a tiger shark perhaps," Kennedy said.
The attack happened near the central resort of Kihei on the south side of Maui. The beach from Kamaole III to Waipuilani Park remains closed to swimmers.