Why are there flies out on the lake?

Question

why would flies be out on the lake? There is nothing out there for them!!

Answer 1

They want to feed the fish?  Probably they are going somewhere, blown by the wind or attracted by a scent.

Answer 2

It's probably a mayfly hatch.  Here's an informative link about them.

http://gorp.away.com/gorp/publishers/pru...