Origami Seashell

The design is created using circular paper.
The circle is folded in half and then pleated through both layers. Afterwards, it’s opened up at an angle and gently re-pressed along the spine, pleat by pleat.
See the link for a short video of the finished model and a side view.
The crease pattern shown in the slides corresponds to a shell opened at a 60° angle, though this can vary.