Awesome project! Great gathering of minds.
I told a diver buddy of mine about OpenROV and he was very enthused and his curiosity led to a very relavent question surrounding midwater navigation below about 40 feet in depth. He asked - Once the ROV has left the depth at which the operators visual contact from the surface disappears and until camera reference to a stationary object is achieved (say the bottom), how is it, that the reference for motion in the intended direction is maintained? The camera view even with lights will likely at best show small particles in the water moving in vectors opposite the ROV's. As a diver he notes that at around 40 feet even in the clearest water and on the brightest day visibility is reduced significantly. A compass and depth display may be very good to have incorporated even if it is just some simple devices in view of the camera that can be utilized for basic navigation in the intended direction. I realize there are other forums that speak to the sensor topics but I thought that navigation in itself is a good discussion subject.