I keep my boat in Northern Brittany (south part of the Channel). As the water
is rather cool, and sunlight is sparse in winter, I use the cheapest self-polishing brand I can find, namely the one sold by SVB
SEATEC - Antifouling STANDARD from 55,90 â‚¬ | SVB GmbH
coating, a bit thicker than the norm (i.e. I cover less than 12,7 m² per liter, about 10 m²)
Done every year.
A hard version (Sprint) is also available
Only a thin band just below the waterline is fouled after a season, plus a very soft slimey covering elsewhere.