
Holopyga fervida
Another "swimming pool victim" and one of my very few images of Cuckoo-wasps that actually got to get a name, thanks to Paolo Rosa:
"It's a female of Holopyga fervida (Fabricius), it is quite common in France. The male is entirely green or blue. The punctuation on scutellum (almost polished) is typical of this species."

Holopyga fervida (Fabricius, 1781) is a species of Cuckoo-wasp (family Chrysididae) occuring in south-western parts of Europe and northern Africa
Similar species: Wasps, Bees, Sawflies And Ants