It sounds like your remote survived the ordeal. It's a good idea to let the remote thoroughly dry out before reinstalling the batteries. Also, contact with water may have allowed the batteries to lose their charge. I'd probably start with new batteries.
In the meanwhile, while the remote is drying out, the Roku app for iOS and Android phones/tablets can be used as a remote control for Roku units. The Roku and phone/tablet need to be connected to the same local network.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X