In 1957, F. G. Jensen and Willard F. Searle, Jr began testing methods for manual and automatic buoyancy compensation for the United States Navy Experimental Diving Unit (NEDU). In their early tests, they determined that manual systems were more desirable due to the size of the automatic systems. Later that year, the Walter Kidde and Co. sent a prototype buoyancy compensating tank for use with two cylinders to NEDU for evaluation. The valves of this aluminium tank system leaked and testing was delayed until 1959 when it was recommended for field testing.