Do not charge it
Charging a wet device can make damage worse. Power off and let a qualified person inspect it.
Water damage
iPhone water damage help: what to do first.
If moisture is suspected, power off, avoid charging, protect your data, and do not assume the phone is safe because it turns on.
Think data first
Photos, messages, and account access may matter more than the hardware value of the phone.
Repair or replace
Compare age, storage, trade-in value, repair risk, and warranty status before spending money.