A submarine discovering a worm, Biremis blandi.

This sea spider, Nymphon leptocheles, is an awesome father- after his mate lays her eggs, he wraps them in mucus and carries them around with a special pair of limbs (ovigers) to protect them until they hatch.

Like many anglerfish, this female doesn't have to worry about finding a mate- those two little fish are males that are fused to her- they get nutrients from her and in turn they provide all the sperm she needs when she spawns (releases her eggs into the water).

These flatworms are hermaphrodites. Those pointy things are their copulatory organs. They 'fence' with them, until one of them succeeds in piercing the other, fertilizing them.

This is a stalked anemone, a cnidarian that lives in the deep ocean. The stalk helps to lift it into the ocean current, where food is more available.

Chimaera, or ratfish, are in the Chondrichthyes Class of fish, which also includes sharks and rays. Like sharks and rays, they have modified anal fins which they use as copulatory organs. To keep a grip on while they mate, they also have spiked balls on their forehead and in front of their anal fins.