This past weekend while fishing in the Swanquarter area we often experienced small flocks of some sort of diving waterfowl that I'm interested in identifying. When we were running along on the boat, flocks resting on the water up ahead of us would take off and seem to run forever and then fly low to the water to keep ahead of us, maybe eventually peeling off to one side or the other and oftentimes diving underwater. Once when drifting along the bank casting for fish we had a flock of about 30 birds come within 100 yards or so of us and I was able to witness an interesting behavior. All within just a few seconds of one another, they would dive underneath the water and disappear for a 10, 15, 20-seconds or so and then all pop up pretty much simultaneously 25-or so yards away from where they went under. I'm guessing they may have been feeding or something. They were mostly a brown color with a lighter (maybe white) patch or so around their head area. Some sort of grebe, perhaps? I can't find any sort of picture on the internet that looks like them. Definitely not a coot or cormorant, though.