|There are about 300 British water mites, and over 900 European species. Identification to species level is very difficult, and usually requires a microscope and complicated keys.
On the right is Hydrarachna sp., a water mite.
Note that the first pair of legs do not have the swimming hairs that the other legs have. It is 5 - 8 mm long.
Hydrachna insert their eggs into water plants using their ovipositors.