Pied-billed Grebe
Grebes are diving waterbirds, able to go down as far as 90'hunting fish or other acquatic dwellers. They can adjust their bouyancy and you sometimes see one showing only its bill above the water. They're built a bit like loons, to whom they're unrelated.

We found this little guy hanging around in the Bosque d'el Apache Wildlife Refuge in New Mexico. (4/07)