Shackles from the deep : tracing the path of a sunken slave ship, a bitter past, and a rich legacy / by Michael H. Cottman. (OCLC #946580015)
RDA 11.0, the purpose and scope section of the chapter on Corporate bodies, includes this clarifying statement (emphasis mine):
Ad hoc events (e.g., athletic contests, exhibitions, expeditions, fairs, and festivals) and vessels (e.g., ships and spacecraft) are considered to be corporate bodies.
so subject headings for individual ships are recording in 610 fields:
610 20 ǂa Henrietta Marie (Ship) ǂv Juvenile literature.
More general terms about types of ships are still topical headings:
650 _0 ǂa Slave ships ǂv Juvenile literature.