Its been asked, but I'll still respond.
Starbrite hull cleaner. wear a respirator, put the stuff in a spray bottle, and mist it onto the hull for best coverage. mist one side (port or starboard) then go back to where you started (to give the solution a few mins to set in) and use a soft bristle brush with some water. It'll come right off.
You'll likely have a few stubborn spots, but just repeat.
http://amzn.to/2xy5wi3
Theres also a gel, but if you use the liquid stuff in a spray bottle, it works better and you use less of it. One bottle lasts me 2 seasons. Each season I clean twice, each time cleaning, I spray the boat twice to get full clean.