That man is 24-year-old Joel Arizza of Lansdowne, Pa.
Another man on the boat, Kevin Kelly, managed to swim to a boat ramp on Flower Street in Chester.
Kelly told police that he and Arizza were out on a 15-foot recreational boat that sank at about 2:00 a.m. Friday.
Search crews found the boat submerged about four miles south of the Commodore Barry Bridge, in the area of the Fox Point State Park in Wilmington, Delaware.
The U.S. Coast Guard and State Police continue the search for Ariza.