Reminder! You control the set point.

Why is this important?

It is possible to move the set point to a value that is impossible for the vehicle to achieve.

How?

Imagine you are in Auto Depth mode near the bottom. If you command the vehicle to dive, i.e. move the set point down, it is possible to keep moving the set point until it is deeper than the bottom. The vehicle of course will stop when it hits the bottom, but the set point may be below the bottom and if you are not paying attention the vehicle will keep trying to achieve that set point.