Now that everybody had a chance to play the subs, I'd like to throw some things out there that I think would help it fit into the main game.

Concealment

It'd probably make sense (as flamu has mentioned in a video as well) if the subs get more concealed the deeper they go (but sonar will always pick them up). It's logical (as is currently implemented) that they get a big concealment boost when going from surfaced to periscope depth, but they probably deserve a gradual increase in concealment as they go deeper.

This would also allow for map design (the seafloor specifically) to influence a subs concealment. It could not be as concealed in shallow waters as it can be in deep waters. Surface ships could select positioning making it hard for subs to sneak up.

Speed

Getting the obvious out of the way, the event subs are way faster than ingame subs should be. A typical WW2 sub would do something like 18-21 knots on the surface and 7-9 knots submerged.

However being at periscope depth should would also incur some speed penalty vs. surfaced. The simple reason being that your periscope is a relatively thin tube sticking out at the top of your vessel, you go to fast, it may get damaged (and you'll need your periscope if you're in a sub).

Then there's also the speed at which you can fire torpedoes. I didn't find documentation of this, but I'm pretty sure launch hatches would jam if you go to fast, so maybe you'll have to slow down if you want to fire torpedoes.

Seafloor

The event currently does not have a seafloor. But I think for submarines to make it to the main game a seafloor is paramount. Not only would it allow (as previously mentioned) to interact with concealment that a sub can attain. The available diving depth can also make it easier or harder to hit a submarine with depth charges (a shallower depth obviously being favorable since you can spread the depth charges over less depth, hence making it more likely to hit the submarine).

Damage

I'd like to suggest that it should be possible to hit submarines with torpedoes not just when surfaced, but also at periscope depth. For deepwater torps maybe even a little below that.

Regarding artillery damage, right now once a submarine is at or below periscope depth, it can no longer take artillery damage. This seems wrong to me on two levels. First it means you can drive around on the surface worry-free, and if anything focuses you, just slip below the waves faster than any shells can arrive. Secondly it's not really realistic that a shell exploding in the water a few meters from your submarines hull would do no damage whatsoever. Submarines should take at least some damage from shells that splash near them in the water depending on distance to the splash.

Matchmaking

There should obviously be some kind of cap (like for destroyers) to limit how many submarines can be on each side (2-3 seems about right). I'm not sure the 12v12 lineup is sufficient to accomodate 4 (and with an increased incidence of CVs after the rework) 5 ship classes. So maybe the format would have to be extended somewhat to like 14v14 if submarines are put into a match.

Misc

• There should be some indicator on the minimap what concealment you will have if you go up or down (it may be pretty important not to go up too soon etc.)
• Depth charges are a bit hard to spot right now, in the main game this being a major threat, subs should have some good visual indications of where they're going down.
• The skill system will really need a rework when subs get into the game, because most skills are useless for them right now. It exemplifies a deeper problem of skill-starved ships (i.e. not having enough points to take the skills that are vital and so ending up having to make some crappy trade offs) vs. skill-rich ships (i.e. having all the skills you need, and not really needing to make any trade offs).