36 CFR 3.18 - May I snorkel or underwater dive in park waters?
(b) In waters open to the use of vessels, a diver must prominently display a dive flag during dive operations. A dive flag must not be displayed unless dive operations are ongoing.
(c) The dive flag must be illuminated when dive operations take place between sunset and sunrise. The dive flag illumination may not consist of lights that may be confused with navigation lights or aids to navigation lights.
(d) While on the surface, submerging or surfacing the diver must remain within a 100 feet horizontal radius of the diver flag.
(e) If State laws or regulations exist concerning snorkeling activities, those provisions of State law or regulation are adopted.