I have ridden PWCs for 20 years and you instinctively hold on and try to shift weight and bring it back to a stable position. Seldom do you just let go and bail even when you are sliding off the side. Most people will turtle a PWC before they give up and let go, especially at slow speeds. At high speeds, it will throw you like a rag doll as it tips and digs in. This guy obviously has all the gear and some motorcycle know how so I'm not sure how he managed such a controlled bailout. It had to be some combination of wet conditions, VSS kicking in, wet gloves, and a touch of stupid.
I'm sure that's what I would have done - hold on at all cost. Bailing out isn't something I learned. Maybe dirt bikers do that instincty? I'm still new on the dirt myself ...