ANSON — A Florida man drowned Wednesday in the Kennebec River after the airboat he was piloting suddenly became upended and sank into the river, according to officials.

Mark Henry, 72, of Fort Pierce, Florida, died when the airboat he owned nose-dived into the river in Anson at about 6:30 p.m., Mark Latti, spokesman for the Maine Department of Inland Fisheries & Wildlife, said Thursday.

Henry was on the boat along with Matthew Sleeper, 63, of Anson. Both men were thrown from the boat and began swimming to shore, Latti wrote in a statement released to the news media. Sleeper made it out of the water, but when he looked back, he could not see Henry.

North Anson firefighters were later able to locate and retrieve Henry’s body, Latti said.

Sleeper told Maine game wardens that Henry had adjusted the airboat’s trim tabs as the men were traveling on the river. The boat then went nose first into the water. Trim tabs help balance a vessel and keep it level.

Latti said that before Henry could correct the problem, the airboat began taking on too much water and started to sink.

Sleeper had done some mechanical work on the airboat, and Latti said a primary focus of the investigation will be to determine if the craft had remaining mechanical problems.

An airboat, also known as a fanboat, has a flat bottom and is powered by a large, aircraft-type propeller. The boats are used commonly in the Florida Everglades and other areas with shallow water, marshes or swampland.