Concerto
Well-Known Member
Half a knot is nothing.That's why sailing upwind in the Baltic is so frustrating. It's not uncommon to have something like half a knot of adverse current, and never anything favourable.

Notice the speed through the water of 7.75 knots and the chart plotter showing 11.0 knots - that is tide. This was sailing down the Northern Ireland coast from Rathlin Island to Bangor, but I did have tide of up to 5 knots against me entering Scapa Flow in a westerly gale. You can read about that hairy day here.
Round Britain day 43