These very strange creatures are Sea Spiders (Pycnogonida) but they are not true spiders, thought they seem to closely resemble them. They are arthropods, as they are invertebrate animals that have an exoskeleton, a segmented body and jointed appendages. Much more intelligent people than me place them closer to spiders than crustaceans, but new genetic evidence seems to suggest that they could be an ancient sister group to all other living arthropods.
So they are a very interesting critter indeed. We do not see them that often, and they come in many varieties. There are over 1300 known species, ranging from tiny (1 to 10mm) to over 90cm (35in). Most seem to live in the Mediterranean and Caribbean Seas, as well as the Arctic and Antarctic….and, of course, Lembeh.
The ones we get here tend to be about 3cm (1 inch) or so in size. They are carnivorous, feeding on anemones, sponges and hydroids. They are great to watch and even better to see close up, as there is nothing else like them here.