Step 1.

Take a square sheet, lay it flat on the table, with the bottom edge horizontal.

additional information

  • If it is two-colored, place the colored ceiling side.
  • The corners of the square are: top left, top right, bottom right, and bottom left.

Step 2.

Make a vertical valley fold by bringing the right edge over to the left edge. Crease well, then unfold.

Step 3.

Make a horizontal valley fold by bringing the bottom edge up to the top edge. Crease well, then unfold.

additional information

  • You have just marked the medians of the original square.

Step 4.

Turn the model over from right to left, then position it as a diamond.

additional information

  • The corners of the square are now: at the top, on the right, at the bottom, and on the left.

Step 5.

Make a vertical valley fold by bringing the right point to the left point. Crease well, then unfold.

Step 6.

Make a horizontal valley fold by bringing the bottom point to the top point. Crease well, then unfold.

additional information

  • We have just marked the diagonals of the initial square.
  • On the sheet, you can feel that:
  • The medians are mountain folds (the median fold forms a ridge)
  • The diagonals are valley folds (the diagonal fold forms a trough)

Step 7.

Bring the top point to the bottom point using the existing horizontal valley fold.

additional information

  • You get 2 overlapping triangular panels, connected by a horizontal hinge edge at the top.
  • On the front and back faces of the shape, two valley folds connect the middle of the hinge edge to the middles of the right and left sides of the triangular panels.

Step 8.

Hold the model between the thumbs and index fingers of both hands so that the thumbs, which are in front, come to touch the middle of the front valley folds, and the index fingers, which are behind, come to touch the middle of the back valley folds.

additional information

  • The fingers of the right hand are just to the right of the right valley folds.
  • The fingers of the left hand are just to the left of the left valley folds.
  • The shape is now no longer on the table.
  • It is held vertically in front of us, with the hinge edge horizontal, and the third point of the triangle pointing toward the table.

Step 9.

Add volume. To do this, push both hands symmetrically downward until the thumbs and index fingers meet.

additional information

  • The shape has opened, and we obtain 4 double-thickness triangular flaps.
  • One to the left, in the left hand.
  • One to the right, in the right hand.
  • One free to the front.
  • And one free to the back.

Step 10.

Tilt the front flap to the left, and hold it against the left flap.

Step 11.

Tilt the back flap to the right, and hold it against the right flap.

Step 12.

Place the model flat on the table; the base of the water bomb is ready.

additional information

  • There is a triangular shape with:
  • A closed tip at the top,
  • And 4 double-thick triangular flaps, open at the bottom.
  • A vertical valley fold can be felt in the middle of the shape, running from the closed tip to the middle of the lower edge. This is the vertical axis of symmetry.
  • The 4 flaps are connected to each other by the closed tip at the top and the vertical axis of symmetry.
  • There is a front left flap, a back left flap, a front right flap, and a back right flap.