The carrier air group has sonar even when the hull does not

Do modern carriers and amphibious assault ships have anti-submarine sonar?

Their air groups can carry anti-submarine sonar on helicopters; navigation or depth-measuring sensors on the hull are a separate capability.

A sensor that measures water depth is different from sonar intended to hunt submarines. Carriers can carry helicopters equipped with sonobuoys and dipping sonar even when those sensors are absent from the hull. In that case, the anti-submarine sonar belongs to the embarked air group. The distinction explains why saying that a helicopter has sonar does not establish that the carrier itself has a hull-mounted submarine-hunting system.