Water Scavenger Beetles

I've seen these bugs on my shallow pond surfaces before. I've even taken many pictures but couldn't figure out what they were. All of the pictures seemed a bit blurry so I couldn't make out features. I did figure out they were beetles but the water beetles in this area are black and these definitely seemed lighter in color. I tried again and found a web-site referring to "silver beetles" - a nickname earned because they envelope themselves in a bubble of air in order to breath when diving. It all came together. The beetles appear silver because of the light reflected off their surrounding air bubble and I can't get a distinct picture because that cocooning bubble distorts the light. Water Scavenger Beetle is just their family name. Until I can capture one, I won't be able to figure out anything more specific - there are hundreds of different species. By the way, these are good guys to have in my ponds - they are voracious mosquito larvae eaters.