 Unlike depth charges, which were launched behind and to the sides of the attacking ship and disturbed the water, making it hard to track the target because ASDIC lost contact, Hedgehog charges exploded on impact.Hedgehog allowed the attacking ship to change course and maintain contact as the target manoeuvred, as well as allowing a normal depth charge attack.Hedgehog solved one of the most pressing problems, keeping ASDIC contact at short ranges.