This fellow was zooming around so fast most of my pictures of him are just a blur, even at a shutter speed of 1/250th of a second. I thought it was a Dytiscidae, until I got home and found it in Dillon & Dillon as a Haliplidae, a Crawling Water Beetle.

Funny that D&D says of the Crawling Water Beetles: "Instead of swimming actively about as do other aquatic beetles, these crawl leisurely and rather awkwardly along the pond bottom or on submerged vegetation."(1) Apparently, mine didn't get the memo on that.

Admittedly, the behavior may be atypical since I had netted him and placed him in a dish without any hiding places or plants to crawl on.

Of the four species pictured by D&D, mine seems to match P. duodecimpunctata; corrections or confirmations appreciated.