Short answers, pulled from the story.
A total of 283 Allied submarines were active in the Pacific and Southeast Asia between 1941 and 1945, of which 61 were sunk. The majority were U.S. Navy vessels, with the British Royal Navy contributing the second largest number and the Royal Netherlands Navy adding smaller numbers.
U.S. Navy submarines were responsible for 56% of Japan's merchant marine losses during the Pacific War. By the end of the war in August 1945, the Japanese merchant fleet had fallen to less than a quarter of its December 1941 tonnage.
The Mark 14 torpedo had four major engineering faults resulting from being mass-produced without adequate testing. It had only a 20% success rate from December 1941 through late 1943. The defects were not fully resolved until September 1943, leaving U.S. submarines largely ineffective for the first two years of the war.
375 officers and 3,131 enlisted men were killed out of approximately 16,000 American submariners who served, producing a fatality rate of around 22%. Fifty-two U.S. submarines were lost in total, all but one in the Pacific theater.
Allied unrestricted submarine warfare in the Pacific was cited as a mitigating factor in the sentencing of Großadmiral Karl Dönitz at the Nuremberg Trials. Admiral Nimitz provided a written statement that U.S. submarines had behaved no differently than German ones, and the International Military Tribunal's judgment stated that Dönitz's sentence was not assessed on the ground of his breaches of the international law of submarine warfare.
Allied submarines conducted reconnaissance patrols, landed and supplied special forces and guerrilla troops, performed search and rescue operations, and carried out mine detection missions. By the end of the war, U.S. submarines had rescued 504 downed airmen from the ocean, including future U.S. President George H. W. Bush.