Water Measurer Hydrometra stagnorum

There are two species of Hydrometra in Norfolk but I believe the other (Hydrometra gracilenta) is restricted to the Broads. My understanding is that this one is identified by the position of the eyes (further down the head) and the more matt surface of the abdomen. I believe this is a familiar species to aquatic surveyor but as one who prefers to keep my hands clean and dry I hadn't come across it before. I found this one under a log on a path beside a lake.

Water Measurer Hydrometra stagnorum, Wendling Beck Environment Project (Norfolk, UK), 5th April 2025