This isn't the only planet to have water on it. There are likely countless other worlds out there covered in the wet stuff. So don't go assuming we'll be the only civilization to have ever come up with the idea of giant sea monsters!
That piece above, plus all the others you'll see in this gallery, are the work of Francesco Lorenzetti, an artist employed at Atomhawk, a studio which specialises in video game artwork.
To see the larger pics in all their glory (or, if they're big enough, so you can save them as wallpaper), right-click on them below and select "open in new tab".