For a sea-focused map, what I would call a mariner's map, I would expect to see wind and ocean currents, depth markers (also called soundings), latitude and longitude lines, reefs and shallows locations, plus notes in the margin for indigenous tribes, plants and animals, plus the above mentioned things like coves, shipwrecks, etc. and possibly some star notations for navigation if the culture is not of a sufficient technology level. Mapping out the geography is the easy part...it's all that detailing that is mind-numbing.

On the other hand, if I were a player, all I would want to know is where the caves and temples are (marked with a big X) so I can go and take their stuff Solid start, just keep at it...I hate detailing too.