Anyone who is in the water in a known surf spot, who is not surfing. Rather they may be standing, splashing, wrestling, throwing a football, being pale white, wearing a t-shirt, floating, oblivious to the vessel headed towards them, in the way.
In the summer time tourist season you might say: "F#@kin bouys, messin up my wave, looking scared shitless when we lock eyes right before I interupt there splish splash session. Yet, they still don't leave".