What dolphins?

Browsing through a book of optical illusions on from a friend’s coffee table I instantly recognised what is probably one of the most famous illusions not drawn by Escher – that of Freud’s bushy muff …

… an image in which I never fail to see the naked body long before the diagnosing shrink.

On the page opposite was a picture titled Lovers Or Dolphins which I hadn’t seen before.

Inevitably the first thing I saw was a pubic triangle … followed by a pair if tits.
It was only after I had read the title, and spent a surprising amount of time, that I noticed even the first dolphin … and that was the one whose tail described the aforementioned pubic triangle.

Knowing there were more such indicators of how obsessed one is by sex, I later hit the internet. Here are some of my favorites.
(In most cases I don’t think these are truly optical illusions, but rather optical puns, not that it matters.)