This water mite is about 2 mm long and the spherical, unsegmented abdomen takes up most of this length. It is probably Hydrachna sp. Many water mites are brightly colored although some species are dark brown or black. The four pairs of legs are segmented; the head has one pair of eyes that are widely spaced and a pair of pedipalps used in eating.

Water mites can swim and crawl and the ones best at swimmers have hairs on the legs. They are usually found in still water near the bottom or on vegetation along the shoreline. They are omnivores, eating such things as insect larvae, small worms, eggs of various species and plants. The larval stage, which only has three pairs of legs, is parasitic on aquatic insects, naiads or even adult insects. Water mites can absorb dissolved oxygen from the water, but they may also crawl to the surface to get air.