Barnacle sex.

Runswick Bay barnacles looking all innocent at low tide. When the water rises, it's a very different story. If you ever wondered how barnacles reproduce, the Oyster's Garter has the answer, and it has some surprising dimensions.

It's respectable to be interested in barnacles: Charles Darwin spent years studying them, and wrote a monograph on the subject (Living Cirripedia, A monograph on the sub-class Cirripedia, with figures of all the species. The Lepadidæ; or, pedunculated cirripedes).