water damage to my Galaxy S6

Disassemble the phone.

Samsung Galaxy S6 Teardown

Clean every connection with a soft toothbrush and Isopropal alcohol.Water will cause the inner circuits to corrode so its important to clean all surfaces and contact points. As well clean the logic board use a 99% isopropal alcohol for all cleaning. Once everything is clean it's time to start drying out the phone. Set the screen in a desiccant or silica gel leave it in for several day moving it from time to time to get the max effect from the desiccant . Use a blow dryer on a low heat setting to dry the rest of the phone this helps to speed the evaporation of the alcohol don't attempt to dry water with the blow dryer. Replace the battery with a new one consider the old ones done.Batteries do not fair well with water. Clean again with isopropal alcohol let dry and when you think everything is clean and dry reassemble the phone (make sure to clean the contacts on the screen after removing from the desiccant). Once you've reassembled the phone its time to power it on. Hold your breath and hope for the best