Identification help for Tuesday night

[KidK9]

Can I get some more ID help. I need scientific names as well as common names. All pics taken in the Caribbean.

For the second pic, I'm looking for help on that crab. Thanks a ton.

 

[TwoBitTxn]

#1 Giant Anemone. Humann doesn't list a genus or species

#2 Channel Clinging crab Mithrax spinosissimus

#3 That looks like the eye of an octopus to me. Common Octopus Octopus vulgaris

 

[maractwin]

#1 The Giant Anemone is Condylactis gigantea. I suspect that the colors on this picture have been tweaked, as I've never seen one quite that purple.

#4 The yellow mass is an encrusting sponge, but I couldn't tell you which. The green algae growing rows of circular "leaves" is Halimeda. Looks like two different species, actually. The ones with the larger "leaves" growing outward is Large Leaf Watercress Alga, Halimeda discoidea. The ones with smaller leaves growing downward are Small-Leaf Hanging Vine, Halimeda goreaui.