In my photo backlog with unidentified garden insects sat this odd duck. Its a water boatman, Hesperocorixa linnaei, a member of the Corixidae family. These bugs resemble backswimmers but as that name says those bugs swim on their back where this one doesn’t.
The bug swam in a green plastic bucket with a layer of water in it. After peddling around some time it took off again.
I can remember these critters from my childhood when I would frequently encounter them in swimming pools in France, where they would be peddeling on the bottom and in the corners where the dirt in the water would collect.