The six-spotted fishing spider (
Dolomedes triton) is a fairly large and semi-aquatic spider that can be found lurking along the banks of lakes and ponds. It will also frequently venture out onto the water by making use of floating plants, and it can also run over the water surface. I have seen them submerge under water as well to escape danger. I do not know if it will hunt for prey under water. I expect that while under water they become covered in a layer of air. I would like to test that, and so this summer I have plans to take some home to briefly view in an aquarium. They well of course be well cared for and then returned to their home.
In any case, a few years ago I had found one that had taken a dragonfly (I think it was a blue dasher dragonfly). It was several feet off shore, but I managed to float it closer to the shoreline for pictures. This picture was taken by lying down in the squishy mud, which I remember as being very comfortable and pleasantly smelly.
Six-spotted fishing spider by
Mark Sturtevant, on Flickr
If you navigate to the picture in Flickr, you can zoom in further and see that these spiders have a dense layer of fine hairs on their body.
