What is "diving bell spider"

n. A spider, (taxlink Argyroneta aquatica species noshow=1), living almost entirely underwater, using hairs on its abdomen and legs to trap air.

The diving bell spider or water spider (Argyroneta aquatica) is one of the few species of spider known to live almost entirely under water. It is the only member of the genus Argyroneta. When out of the water, the spider ranges in colour from mid to dark brown, although the hairs on the abdomen give it a dark grey, velvet-like appearance.