Seeing different marine life generates different emotions in me.
Sharks = awe
Mantas = humility
Shrimps = joy
Sea urchins and jellyfish = anxiety
Large schools of fish = elation
Nudibranchs = comfort

Seeing a nudibranch, flatworm or cerastoma, dwarfed by its surroundings but unmistakable, is like bumping into an old friend.

Banana nudibranch

(click on picture to see more Banana Nudibranchs)

Nudibranchs are actually sea slugs who have lost their shells, making their gills 'naked' - hence their name.

Science Lesson: The Nudibranch is part of the Gastropod category, which is in turn part of the Molluscs. Flatworms are part of a separate category called Polycladida, and tubeworms are part of the Annelida (or segmented worms) category.

By all means memorise these scientific names to impress your diving friends, but I find it easier to just mentally lump them under Squiggly Things.

Glossodoris Atromarginata

(Click on picture to see more of the glossodoris atromarginata)