Just to bring some other experiences in this thread:
Rob Guyett from another old thread on transmitter problems.-
"On the point about dunking Tx's, My son dropped my 6EX 2.4 GHz in the lake (salt water) over a year ago. We pulled the battery out, took the back off, run it under a tap for a few minutes, shook the %$#%$ out of it then left it in the sun for a few hours before trying it out again. Still using it to this day. A club mate has done the same to his 6ex 2.4 TWICE (way clumsier than my son)and his is still going. Interstingly I have seen a couple of other 2.4 GHz radio brands similarly drowned and neither ever worked again. Perhaps they didn't apply the required amount of %$#%$ shaking [:)]"
My experience this weekend.
Turned off AND REMOVED THE BATTERY at once>
Took the back off immediaty and dried it as best I could, poured bottle of water over it and put it in the sun with the wind blowing on it. (did a little of Robs %$#%$ shaking).
Had the car A/C blowing on it on the way home.( not recommended for driving safety)
At home, blew and sucked air through it with a shop vac, and used hair drier.
Then soaked all the electronics with Corrosion X and let it drain and dry again overnight with a fan blowing in it. (other suggestions I have used are Corrosion Block, CRC 666 (656))
Sat all night with the fan blowing on it, tried it next AM and it powered up, then tried with receiver and seems to work fine.
Only thing I think I need to do is replace the shrink wrap on batt pack.(and a safety cord on the neck strap)
Key is to get the power off and dry it quickly.
If salt water more soaking rinse with fresh water.
St Augustine, FL