I work at a marina in the spring, summer and a bit in the fall, so I do a lot of hull washes. Captain phab makes some really good products, so far the best I have found. The one that we use is for professional use only and therefore cannot be sold to the public but it works great, a little hard on the lungs though if not wearing a mask. But they also have other cleaners that are available to the public which work just as well, you just have to let them sit a little longer.