. It is generally the length of the tank and not the diameter that will bother most scuba divers. Carrying the tank without dragging it across the boat dock is a sign that either you cannot carry the weight or your arms are not long enough. If strength is not the problem than maybe the tank is too long. Or if you keep hitting your head on the tank valve and the bottom of the tank is bouncing off of your butt at the same time, than the tank is too long. The two main tank manufacturers (Catalina and Luxfer) both make an Aluminum 80 tank that is 3 inches shorter than the standard tank. They do this by increasing the diameter of this new tank, but it is a little heaver. The Aluminum 63 cubic foot tank is 21.5 inches long. Some of the high pressure steel tanks are only 20 inches in length.