For this exercise, go to the bottom where you have a visual reference. Observe the heading. While watching the display only, turn an estimated 90 degrees and then check your result. After at least 5 repetitions, hopefully with some improvement, move to more open water and repeat. You can be fooled into thinking you are turning more by the water flow introduced by the horizontal thrusters, which tends to sweep water and particles past the camera and make the ROV look like it is turning faster or farther than it really is.