We have to assume the operator knows what he's doing.
I notice he has many surfing videos, so I think he knows what he's doing.
Why do you think this? Just because you see it done in this video doesn't make him a safe pilot that knows what he is doing. Personally I think he is a reckless amatuer that probably has a false sense that - because he's done it once or twice, he will be successful at flights like this in the future. But then, that is the nature of an irresponsible pilot.
Usually when someone like this does crash or cause an accident (and if he hasn't already, he will) - their story begins with a phrase like - "I've done this safely many times and never had a problem so something else must of made it happen" For all the reasons already mentioned, trying to replicate that kind of shot with a drone in proximity to waves, saltwater spray and people, is just a recipe for an accident.