I've rescued kites many times and my technique is always approach from downwind, locate the dump valve visually, and hope for a smooth deflate. I've done the deflate a number of ways. In stable situations, I've gone into the canopy to do the dump (kite in a beach parked manner), or flip the kite on its back, and also (with rider still attached and canopy filled and dragging downwind) reach under and deflate. Then connect my leash to the pump up tether and drag it back in.
Its super dangerous and I'm always ready to bail if it looks like the kite might flip over me.
In a directly offshore situation it would be very difficult or even impossible to drag a kite upwind deflated.
I rescued a kiter being dragged underwater by a death looping kite 2 years ago this way. He was released but tangled in his harness badly. This was my first rescue of the sort and yes its scary approaching a looping kite to deflate it. It was either that or watch the guy die. He didnt speak english, but I could tell he was soooo grateful and I felt like a superstar for sure.
Its always better to get a jetski, boat to do the kite rescue when possible.