Inspect the through-hulls, especially if they are bronze.
Inspect prop shaft, cutlass bearing, stuffing box, prop, zincs, rudder shaft, rudder gudgeons and pintles or bearings.
Inspect and maintain seacocks. Replace if necessary.
Inspect hull-keel join.
Inspect pivot pin and swingkeel/centerboard if necessary.
It would really help if you said what kind of boat you had, as some specific issues may be relevant to your boat.
Inspect prop shaft, cutlass bearing, stuffing box, prop, zincs, rudder shaft, rudder gudgeons and pintles or bearings.
Inspect and maintain seacocks. Replace if necessary.
Inspect hull-keel join.
Inspect pivot pin and swingkeel/centerboard if necessary.
It would really help if you said what kind of boat you had, as some specific issues may be relevant to your boat.