Submersible cruiser?

[Darkwalker]

I guess a light cruiser with 9-12 150mm guns should be doable from a technical point of view. But it would suffer from the same problems that plagues Surcouf, primarily slow dive time. But for possible specs I suggest an upgraded version of HMS X1:

+ 150mm guns in 2-4 turrets. Good enough for raider work
+ Some 20mm guns for AA and suppression work (Similar to the XXI-turrets)
+ small hangar for 2-4 Helicopters (US R4s or a FL-282 derivate) as spotters
+ maybe a small boat dock for 2 "Light S-Boats" similar to the ones carried by the Auxillarie Cruisers

[Kale]

You might want to up at least a couple of the AA guns to 40mm Bofors-style cannon.

[copeab]

I'm surprised that the infamous German Type XI U-cruiser (really more like a submersible destroyer) hasn't come up yet.

[Darkwalker]

Originally Posted by Kale

You might want to up at least a couple of the AA guns to 40mm Bofors-style cannon.

I am quite flexible with the all of the guns. Maybe a version of the german MK-213 cannon (30mm revolver canon, similar to the Mauser Bk-27 of the Tornado) or a similar style weapon as a compromise between weapon weight/size and throw-weight. To be "useable" the sub shouldn't get too large otherwise it has problems in many regions of the world with low water depth that strip it of the ability to dive/dive deep enough not to be seen from the air