I've seen them "mudding", they roll around in the mud and I've heard them making noises while they do it. It's quite a site. My friend and I try to catch them with nets when they do this. But I've also seen them jumping out of the water. It's completley different.
I see it all the time. When we night fish you can be sitting there in the pitch black and then bang you hear something the size of a dog crash out in front off you.