USS Squalus

The Vessel

USS Squalus (SS-192) was an American Sargo-class submarine of the United States Navy, built at the Portsmouth Naval Shipyard, Kittery, Maine, between 1937 and 1939 and commissioned on 1 March 1939. She was 94 metres long, 1,450 tons surfaced displacement (2,350 tons submerged), and armed with eight 21-inch torpedo tubes (four bow tubes, four stern tubes) plus one 4-inch deck gun. Her propulsion was a conventional diesel-electric configuration: four diesel engines for surface operation and two electric motors for submerged operation.

The Sargo-class was among the most modern US Navy submarine designs of the late 1930s, substantially advanced beyond earlier US submarine classes in habitability, range, and operational endurance. Squalus was specifically designed for the emerging long-range Pacific operational role: extended patrols of 60-75 days' duration, long operational range, and sustained submerged endurance.

Her master on her final voyage was Lieutenant Oliver F. Naquin, 35, a career career submariner who had commanded Squalus since her commissioning. Her complement on the final voyage was 56 US Navy crew plus 3 civilian observers from the Portsmouth Naval Shipyard - a total of 59 aboard.

The specific mechanical issue relevant to the disaster was the main engine air-induction valve system. The Sargo-class submarines were equipped with large main engine air-induction valves that admitted air to the diesel engines during surface operation; these valves were required to close reliably before submerged operation to prevent seawater flooding through the induction system. The valves' closure was indicated by an electrical indicator panel in the submarine's control room; the valves' actual physical position was not directly observable.

The Voyage

On 23 May 1939, Squalus departed the Portsmouth Naval Shipyard for her 19th submerged test dive, part of her extended acceptance-trial programme. The planned dive was a routine submerged test at a location approximately 25 kilometres southeast of Portsmouth, New Hampshire, in water depths of approximately 80 metres.

The embarked civilian observers from the Portsmouth Naval Shipyard were present to observe specific performance characteristics of the submarine's submerged operation: diving time, trim control, underwater speed, and communications performance. The dive was scheduled for approximately 08:40 on 23 May 1939.

The ship's position at dive command was at approximately 42 degrees 53 minutes north, 70 degrees 37 minutes west, approximately 24 kilometres off the Isles of Shoals. The weather was fair with moderate visibility; the sea state was calm; the dive was expected to proceed without substantial incident.

At approximately 08:40 on 23 May 1939, Lieutenant Naquin ordered the dive. Standard dive procedure was initiated: hatches closed, diesel engines stopped, electric motors engaged, ballast tanks flooded, dive planes deployed. The submarine began to submerge at a normal dive angle.

The critical mechanical failure occurred approximately 60 seconds into the dive. The main engine air-induction valve had not closed properly when the dive commenced: the electrical indicator panel in the control room had shown "closed", but the actual valve position was partially open. As the submarine's deck submerged, seawater began entering the diesel-engine induction system at substantial pressure.

The Disaster

The seawater entering through the open induction valve flooded the aft engine room and the aft torpedo room at approximately 30 tonnes per minute. The submarine lost approximately 40 tonnes of positive buoyancy within approximately three minutes of the dive command.

Lieutenant Naquin's immediate response was to order emergency blow of ballast tanks and immediate surfacing. The ballast tank emergency blow was executed, but the progressive flooding of the aft compartments exceeded the ballast tank's buoyancy-restoration capacity. The submarine's aft trim progressively increased; her forward section rose while her aft section settled; by approximately 08:45 on 23 May 1939, the submarine was trimmed approximately 10 degrees down by the stern and continuing to sink.

Naquin's second response was to abandon the aft compartments and to close the forward watertight bulkhead door, isolating the flooded aft sections from the still-dry forward sections. The bulkhead door was closed at approximately 08:47 on 23 May 1939, trapping 26 of the 59 aboard in the flooded aft sections of the submarine. The 26 trapped personnel drowned over the subsequent minutes as the aft compartments continued flooding.

USS Squalus settled to the Atlantic seabed at approximately 08:50 on 23 May 1939 in approximately 74 metres of water, her forward section dry but her aft section fully flooded. The 33 remaining survivors (29 crew plus 3 civilians, including Lieutenant Naquin) were trapped in the forward section, with limited atmospheric capacity and no means of surface communication.

The subsequent rescue operation of 23-25 May 1939 was one of the most successful submarine rescue operations in naval history. The specific factor that enabled the rescue was the McCann Rescue Chamber, a diving-bell rescue apparatus developed by the US Navy specifically for submarine rescue at depths up to 100 metres. The McCann Chamber had been developed through 1933-1939 by Lieutenant Commander Allan McCann of the US Navy; Squalus was the first operational test of the Chamber in a live submarine rescue.

The McCann Chamber was deployed from the salvage vessel USS Falcon on the afternoon of 24 May 1939. Over four successive dives (conducted between 24 and 25 May 1939), the Chamber transferred the 33 surviving personnel from Squalus to Falcon. All 33 survivors - 29 crew plus 3 civilians - were successfully evacuated without loss; the final survivor reached the surface at approximately 02:00 on 25 May 1939.

The Legacy

The successful rescue of 33 of 59 aboard USS Squalus was, at the time of its occurrence, the first successful submarine rescue operation in world naval history. The specific McCann Rescue Chamber operation demonstrated that submerged-submarine rescue at depths up to 100 metres was technically achievable; the operational lessons learned from the Squalus rescue were incorporated into subsequent US and Royal Navy submarine rescue doctrine.

The subsequent US Naval Board of Inquiry, conducted through June and July 1939 under Rear Admiral Cyrus W. Cole, identified the specific causes: (i) the mechanical failure of the main engine air-induction valve, which had not closed properly on the dive command; (ii) the failure of the electrical indicator panel to accurately reflect the valve's physical position; (iii) the inadequate pre-dive inspection of the valve's physical state; and (iv) the specific design vulnerability of the induction-valve system to single-point failure.

The specific institutional response included: (i) redesign of the Sargo-class main engine air-induction valves to include secondary closure mechanisms; (ii) enhanced electrical indication systems for valve position; (iii) more rigorous pre-dive inspection procedures; (iv) accelerated development of improved submarine rescue equipment and training. The McCann Rescue Chamber was subsequently standardised across the US Navy submarine rescue fleet and remained in service through the 1960s.

The subsequent salvage of USS Squalus was itself a substantial technological achievement. The submarine was raised from 74 metres depth over a four-month salvage operation from June to September 1939, returned to the Portsmouth Naval Shipyard, reconditioned, and recommissioned as USS Sailfish (SS-192) in May 1940. Sailfish subsequently served through the Second World War with distinction: she conducted 12 war patrols in the Pacific, sank five Japanese merchant ships and the Japanese escort carrier Chuyo (on 4 December 1943), and survived the war to be decommissioned in October 1945.

The specific cultural response to the Squalus case was substantial in the late-1930s American context. The submarine rescue operation was extensively covered by American newspapers and newsreels; Lieutenant Naquin and the surviving crew were celebrated as national heroes; the McCann Rescue Chamber operation was cited as a demonstration of American technological and operational competence in the late interwar period. President Franklin Roosevelt sent a personal telegram of commendation to the rescue operation.

The wreck site of Squalus (now Sailfish) is not of wreck-site status; the submarine was raised and returned to service. The 26 dead from the 23 May 1939 sinking (during the initial flooding) are commemorated by the Squalus Memorial at the Portsmouth Naval Shipyard, Kittery, Maine, and by a memorial plaque at the US Submarine Force Museum, Groton, Connecticut. Lieutenant Naquin died in 1998 at age 93; he had been the last surviving officer of the Squalus sinking.