No worries! I had to really dig to find answers to a few of them…
Yes. The looking is the primary aspect of the explore action, so if you don’t look, you haven’t actually explored, and can’t mark it as explored.
You’ll need one of the handful of abilities that lets you mark an island without docking to place the marker without looking.
Triggering the effect is optional, but if you do trigger it, you must place the ship at a different whirlpool. You can’t bounce around within a single pool just to ditch cargo.
That goes back to one of the earliest entries in the PC (under “Pin”). A ship is still considered to be in contact even if the physical part making the contact is removed. Likewise, replacing/repairing a previously-lost part cannot cause a pin if it results in contact. Some sort of movement must occur to break or create contact.
Their segments do not block their own lines of fire (this is actually the last line in the rulebook under Sea Creatures).
Yes, unless the ship still has some ability to be given move actions without masts remaining (Galley, Oarsman, etc.).
If the ship is derelict and can’t move on its own, it can’t start or continue towing.
Facedown UTs are treated as standard treasure for the endgame condition, even if some/all players know what it is. Until someone picks it up and uses/reveals it to show it has no gold value, someone unloads it facedown at home, or some other endgame condition is reached, the game continues.
No, it loads faceup and has no inherent gold value of its own, so it’s treated just like any other face up non-gold UT (Plague, Fruit, etc.) and will not prevent the endgame trigger. Whatever potential value it might have from making a swap is wasted if you don’t use it in time.