Here's the model I built not so long ago.
Japanese midget submarine used during WWII - Type C Ko-Hyoteki. The one from the kit(Modelarstwo Okrętowe, scale 1/72) portrays an example used in the Attack on Sydney Harbour.
Here's some history:
On the night of 31 May – 1 June, three Ko-Hyoteki-class midget submarines, each with a two-member crew, entered Sydney Harbour, avoided the partially constructed Sydney Harbour anti-submarine boom net, and attempted to sink Allied warships. Two of the midget submarines were detected and attacked before they could successfully engage any Allied vessels, and the crews scuttled their submarines and killed themselves. These submarines were later recovered by the Allies. The third submarine attempted to torpedo the heavy cruiser USS Chicago, but instead sank the converted ferry HMAS Kuttabul, killing 21 sailors. This midget submarine's fate was unknown until 2006, when amateur scuba divers discovered the wreck off Sydney's northern beaches.
More can be found here: https://en.wikipedia.org/wiki/Attack_on_Sydney_Harbour
Photos were taken by my grandson, Kacper(PacificWind). He also did the paint work, stand and rigging.