These two drake Mallards were having a real dust-up. I thought that they were locking bills but the camera reveals they were in fact trying to grab each others breasts, perhaps explaining why one of them looks rather blotchy.
This looks like feathers are being pulled out.
After the first stage they then started thrashing in the water.
And what a splash.
Look at the bill of the bird on the left: I assume this is his tongue sticking out and not a split lower mandible. Do birds have tongues? I guess they do.