Name: Diving bell spider or Water spider (Argyroneta aquatica)
Region: Is found in northern and central Europe and parts of northern Asia
Risk of Extinction: Least Concern
More Info: Is the only known spider in the world that lives entirely underwater. Like other arachnids, it must breathe air, but it provides its own supply by forming a bubble, which it holds by hairs on its legs and abdomen. The spiders must occasionally return to the surface to replenish their air supply, although some gas exchange happens across the surface of their bubbles, so they don’t have to come up very often.
(photo taken from http://www.bbc.co.uk/nature/13614742)