Ground 14 : The electrical potential of the earth's surface. The boat's ground is established by a conducting connection (intentional or accidental) with the earth, including any conductive part of the wetted surface of a hull
NFPA 302 Fire Protection Standard for Pleasure and Commercial Motor Craft, 1998 ed. https://www.nfpa.org/assets/files/AboutTheCodes/30 2/302-A2003-rop.PDF, (Std: Fr Prac for Pleasure and Comm Motor Craft - Amer) {292 NFC}