What are the merits of applying 2 full coat of antifoul as against one ? Of course we will do whatever the customer asks, however our observations are that boats which receive two coats become just as fouled after 12 months as those which receive a single coat plus two coats at the waterline and along leading edges.
Antifoul by nature is very thick; it has various solids and resins that are designed to dissolve out of the paint during its life. This causes the remaining paint to be slightly "brittle" and weak in structure. Over years of antifoul build up, the old paint is prone to cracking or flaking and may simply fall off in patches.