We call them "click beetles." I'm no entomologist so I don't know what they actually are, but I think I know what you are talking about, we get them regularly. If you turn them upside down on the concrete you will see why we call them click beetles! They have a pronounced mandible if i am thinking they are what we get. My daughter rescues them from their watery fate every morning.

http://www.google.com/search?hl=en&c....0.G2_sH-EG2hg

This is an OK picture, ours are similiar...