I think Divers and Raft seem like the most fair events though they don’t really feel like “events” per se. They feel like they should be something like equipment with a one time effect.
Both of those would have been great as equipment. For a point or two more, Divers could even be made reusable. Raft could be reusable too, assuming you went to the island and retrieved it along with the rest of your stuff.
For being called “events”, several of them felt more like crazy magic powers you used to attack your opponents. I agree they would have been much better as global effects that applied to everyone at once, for an entire round, several rounds, or even the entire game. Mechwarrior (also by Wizkids) already had cards that applied planetary conditions to the entire game, so they should have gone with something similar.
Even if they were kept as targeted effects, most of the problematic events could be retooled into UTs without too much difficulty. Becalmed and Cursed Zone could apply around the island where they were found, and could even stick around for more than one turn. Mermaids is already doing essentially the same thing as Natives, Jailhouse Dog (also Kharmic Idol/Pirata Codex) functions similar to Favor, Message in a Bottle has a similar effect to Hidden Cove, and there are several that remove treasure in various ways. Duel… can just go away, or could provide some sort of post-boarding effect.