The signal sent by satellites is reflected off the water's surface, so once submerged, there is no more signal. The GPS navigation system works best when out of the water.

As you can see from the image below, the iX3M2 GPS displays the current point and the target point and indicates the direction to follow using the compass.

When the GPS signal is lost, iX3M2 relies solely on the compass to try and indicate the correct direction. This means that the longer time passes, the more the direction indication becomes inaccurate. The indication becomes precise again as soon as the iX3M2 GPS is able to locate its position again.

The system, therefore, is designed to be used out of the water or when approaching target points with planned resurfacings in order to compensate for course errors due to drift, currents, etc.