Solenopsis, Glaucus Atlanticus, Elysia Chlorotica, Macropinna Microstoma, and Latinus Maximus

Well whoop-de-do.  It's pretty amazing how these little guys band together to form a living raft (complete with air pockets for the submerged ants to breath).  Video here.


Image from National Geographic.

Look at the spectacular Blue Dragon, or Blue Sea Slug:



Another pretty sea slug is Elysia Cholortica, or the Eastern Emerald Seaslug, which is quite amazing because it uses chloroplasts from the algae it consumes to convert sunlight into energy and lives off it like a plant. 

If you're interested in seeing more photographs of nude nudibranchs, National Geographic offers a slideshow and informative video.

And no presentation of random animals would be complete without the barreleye fish that has a transparent head: