In most states it is the Department of Public Safety, State Police. Some states have departments dedicated to boating, some are attached to environmental departments. And the US Coast Guard always has jurisdiction in coastal waters and navigable rivers.
Virginia Department of Game and inland Fisheries, and the Coast Guard on navigable rivers.
The Department of Game and Inland Fisheries.
Department of game and inland fisheries
NC Wildlife Resources
Department of game and inland fisheries
Dmv
The Iowa Department of Natural Resources is responsible for regulating the state boating laws in Iowa.
Virginia Department of Game and inland Fisheries, and the Coast Guard on navigable rivers.
Kentucky Department of Fish and Wildlife Resources is responsible for regulating the state boating laws in Kentucky.
The Florida Fish and Wildlife Conservation Commission (FWC) is responsible for regulating the state boating laws.
The North Dakota Game and Fish Department is responsible for regulating the state boating laws in North Dakota .
Massachusetts Environmental Police
The Texas Parks and Wildlife Commission
The Texas Parks and Wildlife Commission
Indiana Department of Natural Resources.
Louisiana Department of Wildlife and Fisheries