So often we bring you stories of surfers riding atop impressive waves but one photographer is more fascinated with what's going on underneath the swells.
Watch as Mark Tipple explains what got him interested in the underside of waves, showing how he takes the images that look like storm clouds and captures swimmers' reactions:
The Underwater Project by Tipple, 29, was created because he "wanted something different" since photography on top of waves had been around forever. Tipple explains in a feature about the project on his website that he started off snapping shots of empty waves underneath but then transitioned to capturing how people react in the waves because he wanted show "people being real".
Read more about The Underwater Project and Tipple's book here.