Water damage has been known to be a common problem with cell phones for some time now. Water damage can still can cause a significant drop in value and will often void your warranty. Most tablets, including some of the iPad models, have some sort of water damage indicator.
The original iPad has two water damage indicators located on the device. At the time of the iPad launch, Apple referred to them as liquid submersion indicators." Apple has now given them the new name of liquid contact indicators or LCI. The first LCI is located in the audio jack port. Unlike the iPhone and iPod, it is installed much deeper so you will need a flashlight or light-enabled magnifying glass to view it. The second indicator is located inside the dock connector on the opposite side of the pins.
The iPad 2 has no water damage indictors on the device. The easy way to check for water damage on the iPad 2 is to look for corrosion in the SIM card tray.
What to do if your iPad gets wet: