I'm still keeping an eye on Appscope as a source for new and interesting PWAs (Progressive Web Apps) that run under the Edge browser and this one's a very quick Battleships clone. Well worth adding to your favourites or pinning, as described below.
Of course, you can turn this into an 'app' yourself with PAWA or just pin it 'as is' on your Start screen. Or just add it as a 'Favourite'. It's up to you. If you're confused by the different PWA options then check out my feature here.
Here's Waterwars PWA in action:
In portrait mode, the UI is a bit cramped, but see below for the same in landscape (flicking to hide the Windows controls is recommended). It all works as you'd expect, though I'd have liked to have seen visual confirmations when a vessel is sunk. And a basic sound effect or two would have been handy!