"Yes", "No", or "Maybe" to all of the above.

People have built miniature self-propelled torpedoes, even realistic to scale. Whether that's what this guy did, I have no idea.

Can you install an explosive in the space available? Probably. Will it be enough to notice when it goes off? Maybe. Can you build a system to detonate it reliably in a package that small? My Magic 8-ball says, "Not Likely", but that doesn't mean it's impossible.

If you can arm a self-propelled torpedo, & launch it from a submerged R/C submarine, can you even aim it & equip it with an inertial (or other) guidance system, to make sure it goes where it's aimed, so that you can actually hit something at scale range? There's a good challenge for somebody!

All that stuff can be done in small scale, but putting it all together is asking a bit much. I believe some people had all they could handle, making the originals work right in 1:1 scale.

Good luck!

JM