water damage

Leave it off for a few days so it dries out inside. If it still doesn’t work contact Apple support to discuss repair options. Trying to turn it on before it dried thoroughly may have damaged it further.

There's a good chance the phone will need to be replaced. Water and electronics are not good friends. And Apple Warranty does not cover liquid damage (unless you purchased AppleCare+ when you bought the phone). Apple won't usually offer any repair options on a liquid damaged phone. They'll offer you an Out of Warranty replacement, which typically costs about 60% of the cost of the phone when new.