Accidental home insurance would be my first thought.
Next would be taking out the battery, and if competent/confident enough, dismantling of the DS to allow all components to dry (artificially under a low powered hair drier/ left overnight near a heater).
Careful reassembly and a bit of luck from here on in! before inserting battery, power from charger and see if you're getting any lights, try turning on. if that works, insert battery and cross fingers again! good luck!
John R, January 2009