US Naval ships use 110V 3-wire Delta power. I've heard variably that it's for safety (flooded compartments are safer with 64V than 120V live wires) and alternately for reliability in the marine environment (not sure why). Anything requiring wye or 220V, etc, is wired up with a dedicated transformer. The hull is always used as a safety ground; the only equipment that gets wired with an actual safety wire are plastic insulated cases that can't be directly bonded.
Distribution from the load centers is 440/255V delta for HVAC and distribution in general, with final step-down to 110V Delta. All 1-phase equipment onboard the ship (including convenience receptacles) is wired up 1-phase "delta" with two hot wires. This presents surprisingly few issues, despite being the white wire being live (not to mention 110V vice 120V); I can't recall a single issue with any commercial equipment and shipboard power from the neutral being hot.
And yes, it is 110V, not 120, and 440V vice 480. A lot of aircraft use 400Hz (220V wye IIRC, but don't quote me on that), so you see this a lot on ships as well, as it's often cheaper just to use aircraft equipment for a similar purpose onboard ship than to design something specifically for the ship. And no matter how many times I see it, the concept of an electric-powered generator always makes me chuckle
Also, NEC does not apply; the planning yard engineers have final say.
[This message has been edited by SteveFehr (edited 06-10-2006).]