Turn off your phone completely and submerge it in a bowl filled with UNCOOKED rice for 36 hours. Rice is really good at removing moisture from inside of electronics and have saved many devices with this method.
After 36 hours, turn it on and see if the problem persists. If it does, there may be permanent damage and you will have to get a new one.
It is worth noting that unless your S6 is the S6 Active from AT&T, it does not have an ingress protection rating like the previous Galaxy S5. It has an oleophobic coating on the screen and is meant to protect it from small splashes. The phone is not designed to withstand prolonged exposure or submersion to/in steam, fresh water, or especially salt water.