Water is no big deal, the waves are your enemies ! I have broken many sticks due to the action of waves, but never lost a kite entirely. Practice your water flying in higher winds, it makes it easier for the kite to take off out of the water. Use a kite stake... when you land in the water & are unable to relaunch, stake the kite & walk the lines parallel to the water line, pulling the kite gently (!) to the shore. Watch out for the waves... If you pulling too hard, that's how the kite will break, take your time & pull it in slow. It's kinda a give & take procedure, like landing a big fish.
Most of what I said above is related to dual line kites. I've flown 4 line kites in & out of the water all the time, but never had a problem relaunching the four line.
It is super-fun to dunk the kite, let it disappear & then surface & take off ! I rarely come home with dry kites !