Avoid operating your RC watercraft alone - have a buddy along. At least one person in the group should be able to swim. You might be planning to stand on the shore or at poolside the whole time but having (and using) life vests are a good idea because RC watercraft may need to be rescued from the middle of the lake, river, or swimming pool when the battery dies, it goes out of range, or it just quits running.
Don't go in the water until other watercraft (RC or otherwise) are stopped or far, far away. Make sure others know that you are entering the water (swimming or on a boat or raft) to rescue your boat. Don't be the one needing rescue yourself.