Okay, i know what your thinking.  Cardboard gets wet, at which point cardboard sinks… not ideal for a surfboard.  The first thing to point out here is that this project was to create the surfboard core, which is sealed inside a fibreglass coating, making it waterproof.  These photos illustrate the core prior to coating.

The surfboard core is made entirely from reclaimed cardboard boxes sourced from supermarket waste bins.  It is comprised of 320 individual ‘slices’, each cut out on a laser cutter, before being assembled by hand.  Weighing in at a little under the weight of an equivalent foam core product, this surfboard proves the surf industry can really be as environmentally conscious as it claims.