A seacock is a valve with an integral flange. The threads on the "sea" side of the seacock are straight. The threads on the boat side of the seacock are pipe threads.
A ball valve, as I am using the term is just a valve WITHOUT a mounting flange. A ball valve has pipe threads on both sides.
Thru-hull fittings (sometimes called "mushrooms" have straight threads.
Only an idiot tries to mate a ball valve with a thru-hull fitting.