Well, you are assuming there is a beach to get to.Why do something dangerous when it is much easier to go to the beach and land the kite and sort things out safely?
This assumption doesn't hold for everyone, every session.
Of course you need to know when it is too dangerous to try to untangle the lines as well, and how to self rescue....
But when you practice a watersport that requires you to do things you can't do in the water,
you easily become an accident waiting to happen.
So it's at least worth figuring out how to untangle things in the water,
in case you can't get to a safe beach easily.