Sea Spider (class Pycnogonida)

Monument, Lembeh. Night dive.
Yes, the sea also has almost-authentic spiders!
Well, although "sea spiders" are not true spiders, or even arachnids, their traditional classification as chelicerates would place them closer to true spiders than to other well-known arthropod groups, such as insects or crustaceans. This is in dispute, however, as genetic evidence suggests they may be an ancient sister group to all other living arthropods.
And before you ask, no, I don't think they make cob webs :-D
More info here: https://en.wikipedia.org/wiki/Sea_spider