 U-boats could dive far deeper than British or American submarines (over ), well below the maximum depth charge setting of British depth charges.More importantly, early ASDIC sets could not look directly down, so the operator lost contact on the U-boat during the final stages of the attack, a time when the submarine would certainly be manoeuvring rapidly.The explosion of a depth charge also disturbed the water, so ASDIC contact was very difficult to regain if the first attack had failed.