If it is still functioning and under warranty (or you have extended care), take it to an Apple Store. Out of warranty, turn it off, remove the battery,then put it into a bowl of rice for a few days . The extreme dryness of the rice can pull the moisture out. These devices are delicate , if you don't know what you are doing, don't play with its innards :Let an apple tech dismantle it, if you break it you own it, if he breaks it he has Apple behind him.
That said, Take care when you switch it on, there have been issues with the battery shorting, causing it to swell and in some cases explode, though not a frequent occurrence with Apple devices, it is something to keep in mind.