Interesting picture..!
Initially I thought "he's knicked" - especially since the Reg is almost readable on that small shot - the original would reveal all...
However, look at the yacht sailing beyond the seaplane... A yacht (looks about 35') like that will not be a few feet off the beach, but more likely a few hundred feet, if only for draft reasons.
So there's a chance he's actually got his 500' (only 150m) from the jet ski & yacht, and we're seeing the effect of a long telephoto lens... especially looking at the different "focus" of the yacht v seaplane. No need of course to be 500' above the sea...
NoD