waiting for me to fill up the pool

I filled the pool today don’t get excited it’s not Olympic sized it’s plastic, three foot in circumference a pool for my dogs Less than an hour later I see a bunch of flying things swarming the water faeries? bees? wasps? they are thin and fast I walk closer some glide over my head my dog is fascinated attempts to catch them they are too fast for him dragonflies – dozens of them a colony of them; they must have been waiting for me to fill the pool