We don't have synonyms for ship's bells yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are ship's bell and ships bell.
(n) :
The strokes on a ship's bell, every half hour, to mark the passage of time. In each of the day's six watches of four hours, one bell marks the end of the first half hour, eight bells marks the end of the watch.
(n) :
The strokes on a ship's bell, every half hour, to mark the passage of time. In each of the day's six watches of four hours, one bell marks the end of the first half hour, eight bells marks the end of the watch.