The Waterbomb base is a traditional starting point for many models, including the traditional Waterbomb from which it has taken it’s name.
You start by making creases along both diagonals and orthogonals (edge to edge), and then collapsing the paper into a triangular shape consisting of multiple layers.
Taking care when pushing from the sides and squashing will give you the best chance to create a clean Waterbomb base.
Diagrams
1Start with a square of paper, coloured side up. Fold it in half, creasing it, and unfold it
2Fold the paper in half the other way, creasing it, and then unfold it again
3Turn the paper over
4Fold the paper in half once again, this time along the diagonal. Crease it and unfold it again
5Fold the paper in half along the other diagonal, crease it and unfold it
6Fold the paper together, turning the diagonal creases into valley folds. Push the sides at the same time to create triangular layers
