Well, Nintendo recently released the 2.0 update to Steel Diver Sub Wars. It looks like I'm also either the first or one the first people/person to give the info about the updated version. Also, I'm a premium player on the game and you can identify me as T2 on it.

New Submarines
The update adds tons of new submarines (so much so that the game has to load up the new ones when you go the front or end of the collection), including new DLC submarines and two cameo appearances. For the submarines, one of the new non-DLC submarines is unlocked at (holy cow) Level 99. The name of that submarine is the Neptune MK II. Judging from the name, it's most likely an improved Neptune submarine. Some of the already existent submarines were updated, too. By the way, the Neptune MK II is NOT an update that REPLACES the original Neptune. Now, about the cameo submarines. The two cameos are available for purchase at the game's DLC shop. The first cameo is the Blue Marine from Star Fox 64, and since it's FREE, nearly everybody is using it. Plus, it's OP (overpowered) . It has maximum speed when on the surface, but it's OP with it's huge stats. The other is the Giant Z-Class. The GZC (Giant Z-Class) is the final boss from the first Steel Diver.

Hassles
Well, the one hassle is the addition of non-premium players having to pay 2 Play Coins every time they do Internet Mode. Yes, not once, but EVERY time.

Unfortunately
Unfortunately, Nintendo did not take my suggestion of bringing back the Morse-Code Chatroom. Interesting Factoid: The game uses REAL-LIFE Morse-Code! By the way, it WAS NOT an automated reply. I also sent an angry letter to Nintendo before that. Their reply to that wasn't automated, either.

END
I believe that's everything the update included, so that ends this update overview.