Hello.
I would like to see submarines that would be able to swim not only on the water on ships, but under the water on a submarine, even if they will be a small size, you can even be the most primitive to start with. And based on the fact that there is a video where a person found the wreckage of a submarine at the bottom of the sea, it can be argued that the developers plan to add them in the future, whether they are electric or steam engine, it does not matter, the concept itself is to swim under water, where you are not afraid neither storm or pirates.