The new pond

We've built a new pond and here it is almost finished. There's no shortage of water around here but it's a good way to use up some space on what is an untidy bit of the garden and is only used to park cars on at the moment. Not a fish pond so we're hoping wildlife will take up residence - hence the escape rocks in the far corner. Nothing yet other than 3 pond skaters and a few whirligig beetles which arrived within hours of the first water in the pond. How do they know?