I talked with a person in Juneau who runs a rental program with 9 Nordic Tugs. He said he discussed the use of Sharkhide on fiberglass with the "inventor" of the compound. I think he said he lives in Alaska. After the discussion he used it on a couple of his boats and loves it
His protocol was to get one gallon of "On & Off" (muriatic acid) and mix with water in a 2 gallon garden sprayer. Spray the fiberglass (especially bow areas with the dingy tan water stains), let it sit 30 minuites and rinse well.
Then apply the Sharkhide with a soft cloth and THAT'S ALL.
He said one can of Sharkhide will do 2 boats. Not sure I could get 2 boats out of one can and not sure if he was referring to his 32' Tug or his 54'Tug.
I plan to try it this fall due to his first hand testimony BUT...it sounds too easy to be true.