This is not the best photograph in the world but the little beggars are good at diving just as you've got them in focus. It's either this blurry portrait or an even more blurred image of a feathery bum. (No, we're not going to have a vote on it.)
This Australasian grebe (Tachybaptus novaehollandiae) is one of a pair that's nesting on the campus pond. They make it clear to all the other water birds that this is their territory.