We moor Channel Surfing in brackish water, (salt and freshwater) at the mouth of a river.
Bottom paint needs to be re-done every 2-4 years, depending. Having a covered slip keep sunlight off the waterline and helps prevent growth enabling the paint to last longer.
The boat came from the factory with Seahawk AF33 bottom paint. We applied SeaHawk Cukote after 2 years, which is compatible with AF33. That saved us from having to sand off the old paint.
The outboard we bottom paint the transom bracket and nose cone of the Yamaha with Trilux 33.