I dont know about bottom paints preventing blisters but they do prevent algae and growth as indicated below:
From Wikipedia, the free encyclopedia.
Anti-fouling bottom paint is a specialized covering applied to the hull of a boat, designed to slow the growth of organisms that would attach to the hull and affect performance and durability. Other types of coatings can act as a barrier against corrosion on metal hulls, or improve water flow past the hull of a high-performance racing yacht.
In the days of the clipper ships, sailing vessels suffered severely from the growth of barnacles and weed on the hull which, left unchecked, reduced the maximum speed of the ship and also its ability to sail upwind -- both of which affected profitability. Thin copper sheets were nailed onto the hull in an attempt to prevent this. An visible example of this may be seen on the clipper Cutty Sark preserved as a museum ship in dry-dock at Greenwich in England.
In modern times, paints are formulated with toxic copper compounds or other special chemistry which impede growth of barnacles, algae, and other such organisms. Since such a barrier ablates slowly, it must be renewed periodically.
Retrieved from "http://en.wikipedia.org/wiki/Bottom_paint
Why Should I Bother Painting My Boat?
Once fouling has established a hold on a boat hull it will rapidly spread or "colonize" the surface. Prevention is therefore better than the cure of having to remove the fouling by scraping.
There are a number of key reasons to keep your hull free from fouling:
Safety - Heavy fouling growth reduces responsiveness of the craft. The added weight of the fouling can make the boat sit lower in the water than intended. This can have obvious implications in heavy weather conditions.
Protection - Prolonged growth of certain types of fouling can damage the substrate of the hull. For example, the natural glues used to attach organisms to the hull can damage wood and fiberglass. Fouling can also clog water intakes and cause damage to the engines.
Speed and efficiency - Fouling causes drag. As drag is increased, fuel consumption increases and speed is reduced even to the point where a planing hull may not be able to get on plane. For racing boats, this can be the difference between winning and losing a race.
Courtesy Of http://www.yachtpaint.com/
As a matter of fact everywhere i looked i saw nothing about protecting from blisters as one would expect a company to be bragging, if their product was actually good at??