Unknown pond invertebrate

Unknown pond invertebrate

Observation - Unknown pond invertebrate. Description: 2mm in length. Found amongst vegetation while pond-dipping in a large pond in Peterborough. It's very active, sweeping and looping through the water courtesy of whirring legs beneath (can't count them frustratingly!). It's saucer-shaped and looks slightly

2mm in length. Found amongst vegetation while pond-dipping in a large pond in Peterborough. It's very active, sweeping and looping through the water courtesy of whirring legs beneath (can't count them frustratingly!). It's saucer-shaped and looks slightly crustacean-like though.

I normally only see these in July and only ever in this particular large pond. I have often wondered if it's a nymph of some sort. Anyone have any ideas??? It's not in my freshwater guides! Thanks loads for any help or thoughts! (I have a video too).