I'm not interested in cat or watersports. If two players want to do that among their characters, fine, but I won't be initiating.
There is a degree of intentional unrealism in the form of magic. There is a force on the island, perhaps the island itself, perhaps something demonic that wants to corrupt and break humans, not kill them. Wounds will heal faster, including wounds from oversized insertions. There are some cryptids do have oversized cocks, particularly the Pongos. I don't want to put rules on it, but a female character would be in pain for many hours, probably healing overnight - unless she was suffering other injuries which she probably would if she resisted and the Pongo had to beat her up before it could rape her. In that case it might take a couple of days to heal with the magic of the island having other injuries to deal with.
Dire wolves and Wyrms would also have large cocks, but lacking hands aren't really able to get a human being to sit still and would more than likely kill human females... Although it's possible they would spare a human female who adopted a submissive posture, placing her head down, her ass in the air with her legs spread wide. You're welcome to try. It may or may not get your character only raped instead of killed.