Each guy flying on the hose is connected to, dragging, and controlling his own pwc with no one on it. 100% of the pwc thrust is routed to the flying rig, the pwc becomes a floating power unit only. They control the throttle while flying, more throttle means more thrust, and they steer or control flight by directing the smaller jets on their arms.
The other guy in the video was just riding a separate pwc in close proximity.
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Gene :^)
http://www.Strathbelle.com/