The riverboat left from Fort Myers city dock.
About 7:40 p.m., Henderson was walking down a flight of stairs on the vessel when he slipped and fell over the railing and into the Caloosahatchee River, according to the lawsuit.
A “haphazard search” was organized using the staff of the vessel and employees of Suncoast Security, but Henderson could not be located, according to the lawsuit.
Coast Guard crews searched 11.5 hours between east of Cape Coral Bridge and west of Highway 41 into the following day. Additional agencies assisted in the search, including the Florida Fish and Wildlife Conservation Commission, Fort Myers Beach Police and Lee County Sheriff's Department.