After seeing Peppy appear in Steel Diver: Sub Wars, it really was only a matter of time until the Star Fox team's submarine, the Blue Marine, appeared.
If you get Steel Diver premium before Jun 19 (in the UK at least, I will update if other regions) you'll receive the Blue Marine for free! Else-wise, it will be a paid DLC item.
Now if only we can see it return in an actual Star Fox game it would be awesome.
The Blue Marine is available worldwide and can be downloaded immediately if you have premium.
The Blue Marine is paintable in all unlocked paint schemes. It has a crew of 4 and a 4 torpedo capacity.
The sub's stats are speed-focused, at the expense of health. The torpedo reload is quite fast, my guess in an attempt to balance the original unlimited torpedo capacity in SF64, while still retaining a feel for it. The sub's blasters are not usable nor do the torpedoes you fire create a lighting effect.