I always get an incredibly dry mouth and throat while diving. I went to my dentist a few days ago and told them about it, and the dental hygenist told me she had gone to a conference and tried out something new which might help and gave me a sample!. What she gave me is something called 'xylimelts' which is a xylitol-filled mint that has a sticky side so it'll stick to your gums (xylitol helps you make more saliva). The packaging says it should stay put while you're sleeping, so I don't see why it should be too much a worry if you stick it in your mouth while you're diving (probably shouldn't be a choking hazard?). I'll give them a try when next I go for a dive (likely in a week) and post an update if it helped or not.
Here's a link to the website of the stuff XyliMelts for Dry Mouth- Mint Free- 120 discs | OraCoat.com
Here's a link to the website of the stuff XyliMelts for Dry Mouth- Mint Free- 120 discs | OraCoat.com