Additionally, the Balanced SCUBA regulator is dependent on the 1st stage being in the water
at your depth
to provide the ~120psi (increases with depth) pressure in the 2nd stage hose at the ambient pressure. This is the beauty of the design over the old double hose systems that delivered air at only one surface level pressure.
I have used a system as you describe many times to 30 feet and you will notice that it becomes a little more difficult to get a quick breath. When you inhale you have to kinda wait on the air to fill your lungs. Any exertion makes this tough.
Working shallow around the boat is no problem.