Ocean Runners is Cruz Bay recently changed hands. One of the new owners is Captain Jay Rushing. Not me. They will still rent their smaller boats without a skipper. Jay's a good guy and is refitting the current boats and adding some new ones. Give them a shout. They will want the boat back at their base in Cruz Bay every evening.
Nauti Nymph as far as I know requires a captain now. The are Red Hook based but they are the vendor for the Westin on St John so you can get one of their boats there.