I've done a bit of research, and I think there are two main techniques.
The other guys have covered the 'let the kite drift downwind while feeding out the lines then water launch' technique. I guess you have to do this if you're the last one left in the boat, but if the lines tangle, you're a bit stuck with the kite downwind and potentially looping.
If you have someone left on the boat, you can...
- (hopefully on land) run out the lines and attach the lines to the kite
- wind the lines carefully and secure with rubber bands, place bar beside kite centre strut
- deflate kite and roll up normally with bar inside
- (or follow advice in previous replies)
When you're ready to go...
- have someone hold the kite
- you jump in the water with the bar, start swimming and unwinding lines
- When you are fully unwound, launch as normal.
This technique lets you check the lines and abort if there's a winding problem, but you would need a launching area where you won't catch on rigging.
I'm not saying this way is better - it just depends on circumstances - just trying to give you all the options.
Wish I had a cat!!