I expected there to be internal damage to the motor due to hydraulic lock too, especially a 4 stroke being dunked in the water with the throttle wide open. Two strokes are a bit more forgiving. A mate used to run a jetski centre where his hire skis often had to be recovered from the bottom of the lake. Take the plug out, squirt a bit of duck oil down the plughole, spin it over a few times, stick the plug back in and they would fire up straight away.
Fair play to Guy though, he stuck with it but I bet his leathers felt horrible when soaking wet, I'd at least have expected him to be wearing a wetsuit underneath.
and if you didn't see it, it's being repeated on Channel 4 in a minute......