Now I can speculate on the ideal system:
Drop a pattern of buoys and determine their positions and correct the data plot. Detect your target and determine its geographical position. Programme the position in the underwater attack system. Let system calculate assumed target position for intercept.
Release weapon system with its in-flight guidance system to the appropriate point for parachute regarding system so that the warhead enters the water at the correct position.
As the system would have improved on over legacy systems fewer would need to be carried. Given fewer a larger warhead and larger power unit could be embodied.