An essential part of maintenance is cleaning and re-painting the bottom of your yacht or boat. A recent test in Practical Boat Owner magazine found that Seajet 033 Shogun was the most effective antifouling in 8 out of 13 locations in the UK. This is a self-polishing antifouling which is usable on powerboats of up to 40 knots top speed. For owners who need longer protection than 12 months, there is Seajet 034 Emperor or International Micron and, if you want to scrub off afloat during the season, you can do no better than International Ultra which is a hard coating. For aluminium alloy hulls and stern-drives the only option is International Trilux. Any other antifouling contains too much copper and will damage aluminium alloys. There are also more economical antifoulings such as Seajet Samurai but at around £70 for 2.5 litres the clear winner all round is Seajet Shogun. Bottom fouling around Gibraltar is fairly aggressive so you need to apply two coats to be effective from year to year. This is one area where going short is a false economy because bottom fouling causes increased fuel consumption, reduced performance and faster deterioration of affected surfaces, specially if shell growth occurs.