Sorry - no place to get water on either island. You'd have to go to the mainland (Fajardo) to do that. Or top off on St Thomas (e.g. Crown Bay Marina) on the way out and back.

If you want restaurants and bars, Ensenada Honda in Culebra is great - you have to go there first to clear customs anyway. If you want total isolation, Ensenada Honda on Vieques can't be beat.