If you or your kids swim in water over their heads, you should all know how to survive in deep water for long periods. The chances of panic and drowning are reduced when you're trained.
1) Take a big breath, hold it and relax. If you go under water, it's ok, you'll float near the surface. 2) When you need another breath, exhale and kick to the surface. 3) Repeat as long as you like. This method takes much less effort than treading water and you can do it for many hours if you don't panic.