I discovered that we have both kinds of "water boatman" bugs in our seasonal pond. The "lesser water boatman (not shown here) swims at the bottom of ponds and eats algae and aquatic plants, and sometimes eats TADPOLES!!! NO NO NO!! BAD BUGS!! This kind shown is known as a "backswimmer", and is predatory and it loves to eat TADPOLES!! WE HATES THEM WE DOES!!!! NASTY, NASTY WATER BOATMEN!!

If you would like to know more about this bug, Wiki has a great page here: Wikipedia: Water Boatman--Notonectidae