dry mouth??? Please help

I was wondering if someone uses a product to help with dry mouth. I have tried drinking lots of water but that doesn't help except that I want to pee more. When I swim more than around 600 yards, my mouth is very dry. To the point that I start coughing. Now, what I do now is, I turn on my back (or breaststroke) and get my cough out and then turn back around, but from then on, I have to cough so much and I have to keep turning around (or breaststroke), it's not productive.