I was talking some old guy down the boat yard the other week who swears that the best method is to buy the cheapest anti-foul you can and mix chilli powder in with it. He's says that it gives the anti-foul a reddish colour, but works a dream
Just imagine .... there you are, a soft footed barnicle, just resting down on this nice boat when ...
... flamin' 'eck "Chilli City"
Not tried it my self but he has done for the last 15 years
Just a thought - it might do for you