You can try a hail Mary:

1) Take the battery out
2) Cook the key in an oven set on low. Or set it on your dashboard in the sun. Basically you want to get it very hot but don't melt it!

Then put in a known-good battery.

If that doesn't work, then considering you have "nothing to lose", take it apart, down to the circuit board. scrape off any obvious corrosion you find. Make sure to check the battery contacts.

Electronics are generally fine with water. They can be washed and dried no problem. The problem is if they get wet WHILE POWERED (battery in). This is what causes the damage. For example, if you drop a cell phone in water REMOVE THE BATTERY IMMEDIATELY. Then dry it out and it should be fine. Electronic boards are washed in manufacture so they don't mind at all.

Good luck!

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra