Well, then the lifeguard wouldn’t have had to tell him to stay out of the water, would he?
The lifeguard didn’t say, “Get off the beach”; he said “Stay out of the water.”
Once you go into the water, you’re a potential hazard to the lifeguard, not just to yourself.
So the lifeguard’s perfectly entitled to tell SurferDick to stay out of the water.
And SurferDick is NOT entitled to ignore orders from public safety personnel. Under any circumstances, never mind in the middle of a public safety crisis.
TBH, no matter what the ticket says, that was his offense. Responding to safety workers with “Fuck you, I’ll do what I want” should always be slapped down hard, with whatever legal tool comes easily to hand.
(IMnvHO, as someone who spent a decade doing private safety and security at large outdoor festivals.)