If it was fully immersed, there is probably little that can be done. If a minimal amount of water has penetrated it, you may be lucky - try placing it somewhere warm and leaving it for 48 hours to dry slowly, then try again. If this does not work, then it'll either be an expensive repair job, or a replacement on your household insurance.
I've had a further thought - the water may have shorted out the battery, so it may be worth trying with a replacement battery.
Answers & Comments
If it was fully immersed, there is probably little that can be done. If a minimal amount of water has penetrated it, you may be lucky - try placing it somewhere warm and leaving it for 48 hours to dry slowly, then try again. If this does not work, then it'll either be an expensive repair job, or a replacement on your household insurance.
I've had a further thought - the water may have shorted out the battery, so it may be worth trying with a replacement battery.