Nothing, and if it were subtle enough it could be effective at making it drift around. Lots of ways to get a rough fix though, and you don’t need very good abso

Nothing, and if it were subtle enough it could be effective at making it drift around. Lots of ways to get a rough fix though, and you don’t need very good absolute accuracy offshore, using a compass and log to DR your way around. Even better if you have a wind vane and anemometer. The majority of your drift will be wind driven.