Here with a schematic of the Iranian midget submarine class Ghadir.
Described as a littoral water submarine. Green waters close to shore. I doubt even that.
That length in meters about sixty feet [29 meters]. And the displacement about 150 tons.
Compare with a conventional diesel/electic submersible of the German Dolphin class.
Dolphin about twice as long but having a displacement about ten times greater than Ghadir!!
Ghadir having only two torpedoes and no possibility of reload?
It seems no quarters, galley or even a head for that matter. Crew members during a mission not able to sleep, eat, use the toilet?
Well, Ghadir is a vessel the crew of which might even be considered to be fanatics heedless of discomfort or sacrifice.
At the end of the Second World War the Japanese building midget submarines in profusion, the utility of such warships of dubious value I might thing, overwhelming numbers alone NOT sufficing.