@Ben
Can a Hoist’s free explore action happen in between its own move segments? (ex: move S, hoist free explore, move S)
No. It’s an independent action that isn’t applied as part of a move action, so you have to complete the entire move action first (or use it before moving).
If you cancel the Sea Monster keyword, can you still use an L booster like Jerky Johnson to give it +L?
Yes. Even though it loses the abilities of its own keyword, it still counts as a sea monster (ship type) and can still use the Jerky boost.