There is no gravity in orbit/space to pull them toward a certain area so they have full movement and that is why they float
Vt = Vboat - Vriver
Vt = 18 - 2.5 = 15.5 m/s
If the boat's direction is the same as the water, you sum the velocities of the river and the boat .
Because then it could mess up the machine with to much energy
