I was swimming in the Hampstead Heath men's bathing pond, on a cool rainy afternoon. I put my head up and a family of great crested grebes, two adults and a baby, were swimming right in my path so I stopped to stare. It was cute, the baby grebe was climbing onto the mothers back (I cannot tell the sex) then the mother reaches under the water and pulls out a fish. The little grebe rushes forward, and the mother tries to give it lunch. It tries to swallow the whole thing, where they throw their head back and open their mouth. It doesn't quite fit, the fish is larger than it's head. The baby grebe drops the fish back into the water and the father grebe grabs it, and they sort of swim off. I'm not sure if they kept trying to feed the little guy that fish, or if he was sol.