I've seen 2 pair (or maybe the same pair a couple months apart) of what appear to be Bufflehead but could possibly be Hooded Merganser, they're quite small, dive completely underwater, and are quite entertaining to watch. They're especially tiny compared to the 4-6 Mallards that live year-round on the pond, one of those drakes literally is the size of a Canadian Goose! Biggest damn duck I've ever seen.
