If you make it an ability, make sure the ability encompasses most all aspects of ship-life IMO. I'd suggest specialties looking more like this:
Piloting - fairly obvious, steering whatever it is you're in.
Quartermaster - this is managing the ships stores, scheduling watches and crew assignments.
Building - building and maintenance on ships.
Deckhand - all the little odds and ends that don't fit in anything else, like handling cargo loading devices, tieing knots, rowing, using the anchor, etc. (especially useful if you do the advanced rule of substituting specialties with other skills).
Abilities are really broad based and having a skill only be used for piloting (essentially how you've got it laid out) seems far too narrow to me.