Try a hard reset - typically is a combination of 2 or 3 buttons.
Turn power off (remove and replace battery if necessary) hold power and volume + (could be volume - or both volume up and down or a home button with power or 3-way combo on some phones). So hold the volume + and power button together until a menu pops up. use the volume buttons to move up and down and power button to select choices. You want to clean and wipe it. all data will be lost. then select reboot. Google how to hard reset particular phone if this combination didn't work.
If nothing comes on screen upon booting replace lcd as is cracked or If water fried/corroded a connector which has finally worn out can check all connector cables to motherboard. can find...