This guy‘s great!

a.  Predator psychology, he’s totally on it, being neither threatening nor submissive (note the ‘I”m not an idiot prey item, bucko’ avoidance of the nose-bump bite), and then clearly delineating ‘his’ territory with the fluke and tail grabs, but letting go once the shark signals that it’s got the message, rather than telling the GW “game on.”
b.  He’s got his speargun unloaded (note the band hanging loose), so that if a problem comes up, he can stab with it at close quarters, as opposed to thinking he’s going to have the presence of mind to line up a clean shot while being chewed on and shaken around.

Big props.