alcohol or actually.. acetone will lower the temperature at which water evaporates. So that can help. For a temp fix you can try injecting thinned epoxy in the suspect areas or try a product called "git rot". As already mentioned keeping the water out in the first place is the key. Many a boat has been trashed improperly bedded screws or screws that had loosened with time allowing in water.
Wing makes a good point on the temporary fix. I have used "Git-Rot" on wooden boats. Says right on the bottle "Finds and fills seeps and weeps."
Couple of thoughts to consider however.
You will need to remove the wet rot, and get to dry rot...then remove/blow that dry rot gone. Otherwise, you may as well inject a wet piece of double-bubble. The injected slug will eventually cure....but it's just a filler, no strength...with damp surrounding.
If you inject epoxy without addressing the surrounding damp substrate...only serves to allow the balance of the core to rot out faster. You've introduced into the core something solid for the wet to butt up against...accelerating/magnifying the rot.
If it is soft/wet as you describe.....don't waste the money/time/worry/questions/grief. Locate the stringers, cut out the rot, and patch with new AC fir. Glass the new piece, one layer below, three above....bond to the stringers...then the non-skid.
You'll get many years from this solid repair.
