One of the very few advantages of sailing in the Midwest, we don't have barnacles in the Mississippi. They laughingly call it fresh water! However, you guys who say you have to get within 6-8 inches of the prop before you can see it should try my river! 1-2 inches is good on a VERY sunny day! I once told a sailor in the North Channel in all seriousness that if you pour strong coffee in my sailing ground, you will leave a clean spot. But there are no barnacles, only Zebra Mussels! I'm not certain which is worse -- Zebras will close up your thru-hulls and foul your prop too, but probably more slowly. Ever known someone who burned up an engine because the cooling water supply was shut off by zebra mussels? I have, but then, who would expect a power boater to watch his engine temp gauge! It's hard to see little things like that at 50 mph. Do the barnacles close your thru-hulls?