Forecastle — of a Ship is that part where the Fore-Mast stands, and ’tis divided from the rest of the Floor by a Bulk-head; that part of the Fore-castle which is aloft, and not in the Hold, is called the Prow — Harris, John, Lexicon Technicum (170410); to ride forecastle in — i.e. with bows under OED (1989).