This rather lovely little animal is a goldspotted eel, Misyricthys ocellatus, a snake eel from the caribbean (compare and contrast with a red sea version here).
These guys seem able to swim through the sand and mud at will with no extra effort. That soft velvetty looking skin is I presume an adaption to this. They are quite relaxed around divers and I think this is because they have an escape route at will. Their poor sight may be a reason too.