TRURO — The shark that attacked a swimmer at a Cape Cod beach last month was a great white shark, according to Greg Skomal, a scientist with the Massachusetts Division of Marine Fisheries and the state's leading shark expert.

Skomal had suspected a great white was behind the July 30 incident off Ballston Beach in the outer Cape town of Truro, but he said he'd have to interview victim Christopher Myers before determining the species responsible for the attack.

Skomal made the announcement Tuesday, after speaking with the swimmer, examining his injuries and working with the curator of the International Shark Attack File at the Florida Museum of Natural History.

Denver resident Myers sustained severe lacerations to the lower portion of his legs while swimming about 80 yards off Ballston Beach, a town beach located within the sprawling Cape Cod National Seashore. Myers, who was released from a Boston hospital Friday, has appeared on national news programs and has even joked about the attack.

Cape Cod's thriving seal population, particularly along beaches in the lower and outer parts of the Cape, is believed to be responsible for the growing number of great white sharks spotted in local waters. Seals are a favorite food source for great whites.

In recent years, large shark sightings have become commonplace off beaches in Chatham and other parts of the lower Cape, including near-shore sightings in shallow waters.

Skomal is part of a team that's tagging and tracking great whites in Cape waters. Scientists currently are monitoring the movements and habits of nine sharks, including an 18-foot great white.