Price of the paint has ZERO to do with it. Every single
place that you put a boat has different aspects that come into play...i.e. Powerplants, sewage outlets, natural growth. That is the main factor. At the Dock
where (close to the shore) my boat is I use the cheap
CPP Plus as do most of the others there...nobody has a problem. The boats moored in the center of and at the mouth of the harbor all get plastered with everything.
The factor is: there is a outlet pipe from a sewer plant discharges toward the end of the marina which tends to flow out to the center and wrapp out to the mouth.
Old timers used the crappy Bottomshield for years in next door Bridgeport harbor...They were moved up to New Haven Harbor (Steel Point Project) and the stuff just dosen't work there.
If you have the patience and the money you can spend the time figuring out what works in your surroundings or you can ask and look at what people have going that works with your enviroment.
With that said, for extreme conditions (where nothing seems to work) Micron 66 has always been a paint that I have not seen conquered by growth. The downside is the price and please please be careful when sanding
it.....I went to the emergency
room several years ago after a day of removal
...Worst headache I can remember.
The sea and everything in it is unpredictable...do a little research
with your dock
boats and you will save yourself alot of frustrastion.