When the Wright brothers built the first airplane, they used control rods and levers attached to each control surface to fly the airplane. This mode of control went most unchanged until airplanes became more powerful and we required more performance from them. Then engineers developed Fly-by-Wire (FBW) control for planes such that the pilot was no longer controlling the control surface, she was controlling the motion of the airplane. This was implemented through autopilots and allowing the pilot controls to control the autopilots instead of the actual control surfaces. The rationale was simple: the pilot has better things to do than figure out what control inputs were required to execute a precise motion, and computers were better at it anyway.
The same is true with Greensea's FBW system. Pilots have better things to do than worry with what thruster mix is required to execute a particular motion or keep a particular attitude. Greensea's FBW system is a concept of operations rather than a mode of operations and it provides an extremely effective means of vehicle control.
Under most operating conditions, enabling all autopilots (heading, depth/altitude, and station keeping) and using the joybox or on-screen controls to pilot the vehicle is the most effective and easiest means of flying your vehicle. With the autopilots enabled, the pilot flies the vehicle with either the joystick or on-screen controls by controlling the set point of the autopilots. When using the joystick, there is no difference operationally than how the pilot traditionally has flown the vehicle, the vehicle just responds better. Most pilots describe the control as "stiff".
With FBW, operators can significantly shorten the distance between what they are thinking and what the vehicle is doing.
