The operator of the powerboat was charged with boating while intoxicated, Suffolk police officials said.
The victim, a passenger on the 38-foot fishing boat, was identified as Christopher Mannino, 39.
His body was recovered in the afternoon by a police diver in the Great South Bay -- more than eight hours after the 4:52 a.m. crash.
The powerboat, a 25-foot Skater, capsized after ramming the fishing vessel, punching a gaping hole in its side, police said.
Five fishermen were aboard the Silver Bullet, a 1967 Hatteras out of West Islip. Only Mannino tumbled into the water. The others were rescued from the sinking vessel, police said.
Police said Brian Andreski, 26, of Dix Hills, the operator of the powerboat, had a male passenger aboard. Both were ejected into the water but rescued by authorities.
At the time of the crash, the fishing boat, with another following close behind, was on its way to the Bay Shore Mako Tournament, said Gino Giorgini, of Captree Island, a friend of two of the rescued fishermen.
"They are lifelong tournament fishermen," he said.
The Silver Bullet was captained by Richard Leigh Jr., according to his mother, Barbara.
Lou Diaz, 37, of West Islip, took his kids to the Bay Shore marina to watch the boats arrive for the tournament.
The accident, he said, "just puts a chill through your body. You just have to be careful. It's not always safe out there."
With Robert Brodsky, Matthew Chayes and Nathaniel Herz