The next beta version features a new naval unit, the submarine. I don't know if Paradox wanted to include the ship types from Victoria 1 originally or they just copied the techs and forgot to take them them out, but the naval files still had these empty inventions without any effects. So all I had to do is move the inventions to the correct time frame and add some effects.
Submarines weren't widely used before the 1900s, so you need Steam Turbine Ships to invent them. Although they have a high evasion chance, a long firing range and you can get nice torpedo attack bonuses with some inventions after Advanced Naval Design, they are pretty much useless - as they were before WW1. They are slow with weak hull and gun power. So blockading and sinking transports are the only roles they could fulfill effectively.
However after the 1919 techs, everything changes. The more speed, stronger hull and gun power along with more torpedo bonuses turn submarines into a more useful weapon. But because of how torpedo attacks work (only applies vs capital ships) cruisers can crush them. I guess it makes sense considering that light ships were used for ASW.
I really hate how some other mods just put a generic submarine icon there, it looks so out of place. So I tried to make one from the battleship icon, I know it's not that detailed but still better than a picture of a modern submarine. For the animation, I used the files from PDM.
I also added all the icons for the naval battles, which is something that no other mods tried to do as far as I know. The stats aren't final, I will probably balance them in the future.
Those are some cute little icons.