46 CFR §111.05-3

1. (a)An electric apparatus must be designed, constructed, and installed to prevent any person from accidentally contacting energized parts.
2. (b)Exposed, noncurrent-carrying metal parts of fixed equipment that may become energized because of any condition must be grounded.
3. (c)In a grounded distribution system, only grounded, three-prong appliances may be used. Adaptors that allow an ungrounded, two-prong appliance to fit into a grounded, three-prong, receptacle must not be used. This does not apply to double-insulated appliances or tools and low voltage appliances of 50 volts or less.
4. (d)If the installation of the electrical equipment does not ensure a positive ground to the metal hull or equivalent conducting body, the apparatus must be grounded to the hull with a grounding conductor.