5th line is the best and that is what I use.
My experience caught in a squall on 4-line kite (it was and stayed sunny, but wind picked up 15-20kn without warning).
Depower and unhook. Stick butt in the water and body drag to shore with board on my feet (i can let go in a microsecond if I need to)
On beach, release kite to safety leash, detach leash (in case kite tangles and powers up while it's flopping and smashing in the wind, you don;t want it attached to you), attach to footstrap, sit on board and with hands now free bury the board real deep in sand.
Run to kite and deflate.