Most antifouling bottom paints are recommended for preventing hard and soft marine growth in saltwater boating conditions, not freshwater lakes. If you think about it, any bottom paint that works well in high-fouling saltwater conditions would be more than sufficient in freshwater conditions, but, as with an insurance policy, you don't want to spend more money for protection you don't need. In freshwater conditions, you do not usually need to purchase the most powerful (and most expensive) paint. Save your money and look for antifouling paint with just the amount of biocide you need.
To help you determine which bottom paint is best for your freshwater conditions, here are some basic guidelines:
Do you keep your boat in the water all the time? If the answer is yes, you want to consider a hard modified epoxy bottom paint with a medium copper content. This type of paint not only repels hard growth, but is good at preventing attachment of weeds and grasses. Sea Hawk Sharkskin antifouling paint and Pettit SR-21 fresh water hard antifouling paint are good choices good choices for your boat, and your budget.
Do you sometimes take your boat out of the water? If your boat comes out of the water daily, and you trailer it, you really don't need bottom paint at all. But if the boat comes out of the water periodically and you store it on a lift or trailer, the best choice would be an ablative antifouling bottom paint. These paints release biocide as the boat moves through the water. To reactivate the ablative properties, just do a light scuff sand with an abrasive pad before putting your boat back in the water. Good choices for economical ablative paints in these conditions are Sea Hawk AF-33, TotalBoat Underdog, and TotalBoat JD Select.
Do you race your sailboat in freshwater conditions? Interlux VC17 Extra is a low-friction, thin film antifouling paint ideal for freshwater racing/performance.