According to my advanced calculations using Mathematica and hampster wheel drag curves, it will take this nut 5 months to reach Europe assuming he continually sets correct ferry angles, otherwise he'll end up either north of the arctic circle or see penguins in Antarctica.

I will be back and ready to surf in 2025, Bill H

Backwards surfing requires a lot of bracing until you spin around and go forward. Bill H

I'm not forgetting that. At a 45-degree angle to the wind, traditional sailboats can reach about 50%-75% of the wind speed, while advanced racing designs can exceed the wind speed under favorable conditions. So, conservatively, let's assume the 50% case. That is, the sailboats will be going at 2.5 knots at a direction of 45 degrees off of the east direction. So, the component of speed in the east direction will be 2.5 divided by the square root of 2 which equals 1.77 knots. So, adding this to the speed of the river (5 knots) the easterly speed of the sailboats will be about 6.77 knots. Of course, a zigzagging set of tacks will slow the average additional tacking speed down (because it takes time to tack) to less than 1.77 knots. But as long as it's more than 0 the sailboats will go in a east direction of more than 5 knots. If I were wrong sailboats would never race in close loop races. BTW, in races according to sailboat design, racers would choose the tacking angle that maximizes their speed upwind.

Are you ignoring the fact that the tacking sailboat in heat 1 is zigzagging downstream at say 45 degrees hense covering the kayaks distance times the square root of 2?