This is for the iPhone but I suspect it would be similar for an iPad. --> If you see a liquid-detection alert on your iPhone - Apple Support
"When you connect a Lightning or USB-C cable or an accessory to your iPhone XS, iPhone XS Max, iPhone XR, or later, your iPhone can warn you if there's liquid in the connector.
If you see one of these alerts, your iPhone has detected liquid in the Lightning or USB-C connector or on the cable or accessory. To protect your iPhone and the accessory, charging and accessory connection are unavailable until the connector, cable ends, and the accessory are dry."
"If your iPhone or Lightning accessory is wet"
See the instructions about drying an iPhone.
"If your iPhone and Lightning accessory aren't wet
- If you see this alert every time you connect a certain cable or accessory, that cable or accessory might be damaged. Contact the manufacturer.
- If you see this alert every time you connect an Apple Lightning cable or accessory, contact Apple Support" by clicking on this link --> https://getsupport.apple.com/?caller=kbase