36 C.F.R. § 3.21 Swimming and bathing.
Title 36 - Parks, Forests, and Public Property
(a) The following are prohibited: (1) Swimming or bathing in locations designated as closed. (2) Swimming or bathing in violation of designated restrictions. (3) Swimming from vessels which are underway, except in circumstances where a capable operator is on board and all propulsion machinery is off and/or sails are furled. (b) The superintendent may prohibit the use of flotation devices, glass containers, kites, or incompatible sporting activities within locations designated as swimming beaches.
Title 36: Parks, Forests, and Public Property
PART 3—BOATING AND WATER USE ACTIVITIES
§ 3.21 Swimming and bathing.

