I have written a lot about this subject, but I guess people are too lazy to search past posts. So, i will briefly repeat what I have said in the past. There basically are two types of bottom paints. Single season and multi-season. Single season paints are wonderful coatings until you remove the boat from the water and let the hull dry. A chemical change takes place that renders the copper biocide not so effective. Also, with single season paints, the biocide sloughs from the paint leaving the paint on the hull so that when you look at bottom paint with a single season paint job, you cannot assume that there is antifouling protection left. Multi-season paints don't have adverse results when pulled from the water and the hull dries. Also, the biocide and the paint leach away at the same time so that eventually all the paint will be gone and of course when you start seeing bare hull, it is time to recoat. Multi season paints work like a bar of soap. As you wash your hands, the bar gets smaller and smaller, but still cleans your hands. So, the nature of a multi-season paint is that like a time capsule in that it releases the biocide as the paint diminishes. This is good because you don't get a build up of paint like that of a single season paint where the paint keeps building up yet the biocide exits the application. It is recommended that more coats be applied (like 3) of the multi-season paint (and 2 of the single season paint). Multi season paints generally are more expensive than single season paints and so when you apply more coats, the cost is higher, but it lasts longer. In tropical areas, where the boat stays in the water for long periods of time, preferred bottom paints would be Pettit's Trinidad or Interlux' Ultra. They have the highest toxicant percentage and are single season paints. The more toxicant the greater the expense. It makes no sense to buy bottom paint for a high growing tropical area when you sail in a lower growing area of hull build up. That is a waste of money for sure. Things to consider when comparing paints, other than what I wrote above, is, of course color choice and the square footage any given paint will cover. One paint might be cheaper, but how many square feet does a gallon cover? VC17 is yet another type of paint, commonly used by racers, because it doesn't build up, is fast because of the smooth surface due to the nature of the paint (a teflon like component), yet it is a single season paint and must be applied annually after the hull dries for winter storage. It comes in a fresh water and a salt water formula and no one will believe me, but the formula made for the big box stores is different from the same paint made for non-big box stores. Hence they can sell it cheaper. VC-17 is particularly effective against zebra mussels, BTW, which is a growing concern for many fresh water sailors. Also to consider what affects bottom paint performance is the ambient waters the boat is kept. For example if there is a lot of industry in your area, the contamination in the water may inhibit the usefulness or length of antifouling protection you can expect. That is bottom paint 101. There are other subtleties that each have, like slime preventers, etc. Have fun painting. Wear protective clothing and follow the instructions so that you don't waste your money on a paint job that falls off because you didn't properly prepare the hull, or you put incompatible paints on top of each other. It can be a nasty job. Perhaps a boat yard is a better alternative to do the job unless you are a scrappy, hard working boat owner who doesn't care if you look like a Smurf when done.