Aground

Aground means a vessel’s hull or keel is resting on or touching the seabed, riverbed, or shoal so it can no longer float free. Grounding may be intentional (beaching) or accidental (loss of underkeel clearance, navigation error, or dragging onto a bank). A vessel aground in a fairway shows, by day, three black balls in a vertical line and, by night, anchor lights plus two all-round red lights, under COLREGs Rule 30. Refloating may need lightering, ballast adjustment, tugs, or a rising tide.