Sorry if some of these are obvious or repeats.
No worries! I had to really dig to find answers to a few of them…
Does a ship with an Explorer have to look at coins when it docks and explores or can it just mark the island explored?
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.
Do you have to place a ship at a different whirlpool when the Whirlpool UT is triggered?
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.
If a ship is only in contact with a ship stealer such as the Harbinger by the jib/foremast which is subsequently removed, is that ship still considered “in contact” with the Harbinger because that was the previous state of touching? Similarly, does a mast elimination remove the state of being pinned? (ex: a titan takes out a mast from a ship it pinned in place, and that mast was their only point of contact)
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.
Do sea creature segments block other segments’ lines of fire? (ex: a titan shooting forward of itself with the outer arms will have a hard time)
Their segments do not block their own lines of fire (this is actually the last line in the rulebook under Sea Creatures).
Does derelicting a towing ship break the tow?
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.
What are your thoughts on a situation where an optionally loaded UT like Homing Beacon is left on a wild island, only one player knows this and wants to call the game because it’s not worth a gold value? (not callable but this is really interesting given HI Raiders/etc.)
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.
-On that point, does Wine have to be on a home island for the game to end?
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.