Yes, that is historically correct
As the war progressed, ASDIC became more efficient near the surface, as passive listening also, but ultimately never efficient enough to prevent an U-Boat from penetrating the escort (Though running at peri depth meant in turn big chances of being spotted by aircraft). What in turn defeated the U-Boats was their unability to move quick underwater and place themselves in the proper position to penetrate the screen at slow speed. Forced down by aircraft, the only successes scored in late war came by aggressive commanders who by pure luck found themselves in the ideal position (in front of a convoy) to slip through the escort screen at silent running. And even then, once they attacked they would usually be unable to get out alive as they also lacked the necessary underwater speed for that :hmm: