Colorful nudibranch (Indonesia). This nudibranch actually eats stinging/poisonous corals, and rather than digesting them, is able to transfer the stinging cells into the tips of its "spines" so that anything that tries to eat/nibble on it gets a sharp dose of stingers!
Nudibranch (Indonesia). This unusual "nudi" is apparently very rare. Not only have I never seen another one like it, but several nudi experts say they never have, either. Note its external gills in a flowery formation at the top (the nudi's rear).