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The shape of the DC causes a 360o explosion so unless set in a pattern would cause little or no damage unless in almost direct contact with the sub, Two kinds of DC were used proximity ( standard DC ) and contact ( hedgehog )

"Blind Time" is the time between when a weapon is launched and when it reaches the target location. In addition, most early sonar systems lost the target submarine on close approach, usually requiring a "sprint" to reduce blind time. For depth charges, this meant that they were dropped or fired after the sonar contact was lost. Hedgehog was the first "ahead-fired" weapon that could be used while the attacking ship still had sonar contact on the target submarine. This reduced the blind time by two-thirds when compared to depth charges.
The USA built a total of 622,128 depth charges between December 1941 and September 1945. This figure does not include Hedgehog, Mousetrap and experimental units not placed in service use. Over half of these depth charges were still on hand when hostilities ended.

ASW effectiveness during World War II
In the first few months of the war only 5 percent of all depth charge attacks were successful. Normal combat conditions reduced that figure to 3 percent. Combat records showed that in early 1942 the lethal probability of a single depth charge pattern (barrage) was about 3 percent and five attacks would raise the chance of a kill to about 10 percent. The possibility of inflicting significant damage to a submarine was about 30 percent after five attacks. By the end of 1943, better weapons and tactics had improved these figures such that about 30 percent of all detected submarines suffered at least some damage and 20 percent were killed. By the last year of the war, at least 35 percent of the submarines attacked were damaged while 30 percent were killed. In mid-1944, the USN was claiming an 8 percent kill rate with a single Hedgehog pattern. By the middle of 1945, that figure had risen to 10 percent.
In the Atlantic Theater, US surface ships sank 60 submarines, shore-based aircraft sank 54, ship-borne aircraft sank 32 and 40 were destroyed by bombing raids on yards and bases. In the Pacific Theater, surface ships sank 60 Japanese submarines, shore-based aircraft sank 3.5 and ship-borne aircraft sank another 9.5.