33 CFR 329.4 : Navigation And Navigable Waters (§ 1.01-1 To Parts 404-499) — (Parts 200-202 To Parts 404-499) — Corps Of Engineers, Department Of The Army, Department Of Defense (Parts 200-202 To Parts 386-399) — Definition Of Navigable Waters Of The United States (§ 329.1 To § 329.16) — General definition.

Navigable waters of the United States are those waters that are subject to the ebb and flow of the tide and/or are presently used, or have been used in the past, or may be susceptible for use to transport interstate or foreign commerce. A determination of navigability, once made, applies laterally over the entire surface of the waterbody, and is not extinguished by later actions or events which impede or destroy navigable capacity.