I'm not taking a side, but here are a few thoughts about CAC's un-depth charges. I would envision the device being cylindrical rather than round, with a flotation chamber in one end, so when it reached the surface it would float with the explosive charge slightly submerged. We might consider how far out of the water it would extend, i.e. how visible it would be. Its value might be as much deterrence, forcing the attacking ship to avoid it, as actual infliction of damage. Even a small hole near the waterline would be serious for a destroyer or escort size vessel, especially in the open ocean. It would likely prevent them carrying out attacks or steaming at high speed. The device(s) would need to move clear of the submarine quickly, either just by buoyancy or by the release mechanism pushing them away. We would probably want some delay in arming the weapon, either a timer or a depth sensor that only activates near the surface. There would also have to be a second arming mechanism which would keep it completely safe until released. One can't take a chance carrying explosive charges just outside the pressure hull; an unplanned detonation would likely be fatal. All these controls would have to be operated from inside the boat, similarly to the external torpedo tubes on many submarine classes including the Type VII. A couple of posters have posited the submarine running straight away, with the attacker in pursuit, but another tactic might be to turn a bit and lay a line of several mines, then reverse the turn to put the mines between the sub and the attacker. I don't know the details, but I recall reading that having the torpedo tube outer doors open at too great a depth/water pressure could damage the torpedos; that might be an issue for our hypothetical mines.