Another good question.
My opinion (for what that's worth) is that you could target an island since it would be considered adjacent for movement (if you had a sea move available).
And "no" I don't think having an available sea move should be a requirement since this isn't movement or battle.
But I could be wrong...
Right. I wish Grant would chime in. Also looking for that answer on my movement question. It's the weekend though, I'm sure he'll get around to it.