It's simple, you are crossing a river that is travelling at 5 kts. You are motoring at 10 kts. If you want to travel directly across the river you turn 45 degrees up river. Now 5 kts of forward speed is countering the current and 5 kts is taking you across the river. Simple geometry. Straight horizontal line across the river and a straight diagonal line through the water. No arcs. Just because you have learned techniques that give you the visual look you want in competition, doesn't mean you actually understand what is happening. I know a very successful shooter that honestly believes that the bullet initially climbs when it leaves the barrel then starts an arc down as it slows (loses lift.) This misunderstanding doesn't make his ability to shoot accurately any less real.