33 CFR 2.34 : Navigation And Navigable Waters (§ 1.01-1 To Parts 404-499) — (§ 1.01-1 To Parts 121-124) — Coast Guard, Department Of Homeland Security (§ 1.01-1 To Parts 121-124) — General (§ 1.01-1 To § 27.3) — Jurisdiction (§ 2.1 To § 2.45) — Jurisdictional Terms (§ 2.20 To § 2.38) — Waters subject to tidal influence; waters subject to the ebb and flow of the tide; mean high water.

(a) Waters subject to tidal influence and waters subject to the ebb and flow of the tide are waters below mean high water. These terms do not include waters above mean high water caused by flood flows, storms, high winds, seismic waves, or other non-lunar phenomena.

(b) Mean high water is the average of the height of the diurnal high water at a particular location measured over a lunar cycle of 19 years.