Animal metaphor for male masturbation

The former. Ideally into an organism but if there’s enough external stimulation, as one could imagine with certain species of sea anemone, that could also work.

I cannot believe I am replying to this thread, but…how about fungi? Many are rather phallic, but some are invaginated, so to speak. Like trumpet mushrooms. I imagine the texture would be passable.

Have a look.

“Are you looking to find some sort of organism for a human male to masturbate into…”. Answer from the OP was yes. Sheep have been the age old “go-to”.

<insert Scot/shepherd joke here>