Mayflies in a hurry
I guess when you live the short life of an Ephemeroptera, you don't want to waste any time getting started.
Check out this video of mayfly eggs hatching within a minute after being laid - courtesy of the Stroud Water Research Center, video credit David H. Funk.
https://www.youtube.com/watch?v=gtXX9J7iZQA
They're not all as fast as this species, Cloeon cognatum. It's more common for mayflies to take weeks or months to hatch from egg to larval stage.