Depending on the speed of your boat, and especially on very fast boats, a minimum distance is required to place your first waypoint. This security is set up so as not to interfere with the calculation of your boat's progress in game, and to avoid any form of malfunction when reaching this first waypoint.
This minimum distance is directly related to the speed of your boat, so it changes according to where you want to place this first waypoint. The distance limit is represented on your screen as a circle. It changes in real time as you move the waypoint around.