Defending fleets and ports against Kaiten submarines

How did the Royal Navy plan to defend against Kaiten-style kamikaze submarines?

It would combine harbor barriers and patrols with standard destroyer, sloop, ASDIC, and hydrophone defenses at sea.

The exact response depends on whether the manned-torpedo or midget-submarine threat is inside a port or in open water. Harbor defenses combine anti-submarine nets, patrol trawlers, divers, hydrophones, and ASDIC searches to create several chances of detection. At sea, destroyers and sloops apply ordinary anti-submarine tactics rather than treating the Kaiten as an entirely new category of weapon. Protection combines barriers, sensors, inspection, and mobile escorts in several layers.