Much has been said about the relatively low rate of losses for the USN Submarine Service in WWII when compared to other navies. The most common explanation given for this situation is the comparatively inept and lackluster ASW efforts on behalf of the IJN. While this is certainly true, one other factor must be considered. The USN fleet boats were extraordinarily tough and resistant to fatal damage. When you threw in the never-say-die attitude of the well trained and experienced crews, the IJN either had to get in a very lucky shot, or wound up having to pound the living crap out of these boats to get them to sink.
Why was this? Manufacturing facilities in the United States were very modern in the 1940's. The latest technologies and techniques were being employed (such as welding) and this allowed a break with the processes of the past. Having just pulled themselves out of the Great Depression, the workers employed at these plants were very motivated to put out a quality product (they wanted to make sure they kept their jobs!). Management practices were also the best in the world, keeping the workers happy and productive and the plants humming a peak efficiency.
The result was a high quality product. The fleet boats were some of the most technologically advanced and refined submarines of the era. Production quality was very high from all facilities (Cramp Shipbuilding being the sole exception) and lessons learned and new technologies were incorporated fairly rapidly. Electric Boat did tend to drag their feet when it came to working in new gear to the boats, but pressure from the operating forces and the Navy made them see the light. Build quality, however, was never in question.
Today I was doing some web surfing and came across some war damage reports that highlight the toughness of the fleet boats. It is very interesting reading. There are some great photos and very informative color plates. Some of the passages in these reports give me the shivers because I know what conditions inside these boats must have been like.
Report of the USS Kingfish (SS-234) damage from depth charges off Formosa, 23 March 1943. This attack damage was one of the prime factors leading to the deletion of the access hatch in the aft bulkhead of the conning tower.
http://www.ibiblio.org/hyperwar/USN/...8/WDR58-5.html
Report of the USS Tunny (SS-282) damage from depth charges off Palau, 26 August 1943.
http://www.ibiblio.org/hyperwar/USN/...8/WDR58-6.html
Report of the USS Scamp (SS-277) damage from aerial depth charge off Mindanao, 7 April 1944. I quote the following from the report because it is extraordinary: "
The deformation which occurred to both the inner and outer hull structures as a result of this attack is the most severe known to have been survived by any U.S. submarine during World War II."
http://www.ibiblio.org/hyperwar/USN/...8/WDR58-9.html
The next one is the report of the damages sustained by the USS Salmon (SS-192) from depth charges on 30 October 1944. This is one of the most incredible stories of survival that I have ever read.
http://www.ibiblio.org/hyperwar/USN/...8/WDR58-7.html
In all of these cases the superb construction quality of the boats and the nearly superhuman efforts of the crew brought the boats home. If the IJN had been slightly more persistant, we could very well have lost four more boats.
Now, for an example of what it really takes to sink a fleet boat, take a look at this report. It concerns the USS Tang (SS-306) and her loss to a circular run of a Mk 18-1 torpedo. The fact that anyone survived the catastrophic damage she endured is testament to the well trained and disciplined crew.
http://www.ibiblio.org/hyperwar/USN/.../WDR58-10.html