Well, I painted the bottom of my Avon
with two coats of Aquagard and kept it in the water all summer. As of last weekend, the bottom was almost completely clean, with only a bit of slime here and there, and that came off very easily with a dobie pad and a garden hose.
The only issue in applying Aquagard is that on a hot day it evaporates quickly, even though it's water based. By the time I got to applying the second coat it was pretty thick (it still went on OK). So you need to keep it tightly covered and in the shade. There are no thinning instructions on the can, but the manufacturer told me that it can be thinned with a little water.
Overall, I'm a convert--it's a great product and the tech support is very good also.