Nudibranch loves 69

This is a pair of Nudibranch, Halgerda wasinensis mating. Their mating position is side-by-side as their genitalia is located on the right side of its body.
Nudibranchs are hermaphrodites, meaning that they carry both male and female reproductive organs. Moreover, when they mate, they can perform the male role of donating sperm and the female role of receiving sperm at the same time. This process involves two penises and two vagina-like organs, and sperm transmission effectively happens simultaneously during the encounter.