If you and your friends come sit on top of me while I am surfing alone, you are a kook

If you put other people in danger with disregard of etiquette, you are a kook

If you start fights while surfing, you are a kook.

If you make a scene and can't shut the F*ck up in the water, you are a kook.

If you don't respect the locals and each other in general- you are a kook.

If you make more jokes than turns in a session, you are a kook.

however...
If you look like a dweeb and are on a cheesy board, then you are probably just a Barney.