This medium-sized spider (legspan maybe 20 mm) lives on the surface of water pools formed by the outflow from geysers and springs in Yellowstone National Park. The warm water also supports a type of bacterial mat, which you can see on the bottom, several mm underneath the spider.
This one was photographed in the outflow from the Grand Prismatic Spring. Here's the habitat, with Excelsior Geyser in the background and the spider hiding just off extreme bottom of the frame.
These are strictly arms-length shots, holding a Canon A710 just above water surface under the boardwalk.
There was also a small water beetle whizzing around under the surface a couple of centimeters away from the spider. But the beetle was only about 1 mm in length and I couldn't get anything decent of it.
Hope you find these interesting!
--Rik
The amount of pathogenic amoebae must be astounding, not to mention other thermophelic beasties living therein. Of course your spider too is quite interesting as to how it must be able survive in such an environment, along with water beetles and such, an ecosystem worth years of study and research I can imagine on an amateur scale. I cannot help but to imagine that places like this, is where it all began for life on earth. Very interesting there Rik. In my travels many years in the past now, I never had the chance, though I could have, to visit Yellowstone. So many past regrets, as they say hindsight is 20/20. Looks like a wonderful time. Thanks! 
