This thing did wonders for my little nitro, I hardly ever wash my boat (It's 20 years old) but when the probably 40 trips worth of water stains got pretty noticeable it took maybe 10 minutes to have the boat looking one color. Wish they sold a bigger bottle, used 3 quarters of it on a 16ft hull.
Oxalic acid will do the same but for a lot less money. You can mix it in a pump up sprayer and it’s a no touch clean. I bought a 2 lbs bag for like 20 bucks. 3 years later might have used half of it. Also easier to do an entire hull with a pump up sprayer.