This is how you start out making the traditional origami Waterbomb and that is where this base gets its name.
1) Start out with a square colour side up and Valley Fold it in half
2) Crease it well and unfold.
3) Fold the square in half vertically now.
4) Crease it well and unfold.
5) Turn the paper over and rotate it 45 degrees. Fold it in half horizontally.
6) Crease it well and unfold it.
7) Fold it in half vertically now.
8) Crease it well and then unfold it.
9) Now you have all the base creases you need. Start pinching in the left and right sides following the existing creases.
10) Pinching in the sides…
11) Flatten everything following the existing creases. The paper should go where it’s supposed to go.
12) The completed Waterbomb Base.
If you open the paper up you’ll see the following Mountain (black) and Valley (red) folds.