For more than half a century, famed explorer Jacques Cousteau filmed throughout the Mediterranean, offering the world a first glimpse into the mysterious realm under the sea. Now, his youngest son retraces his father's footsteps with renowned marine ecologist Enric Sala, comparing the Mediterranean today with imagery first captured by his father all those years ago. Cousteau was concerned that pollution and over-fishing would end up destroying the fragile sea. Now, the next generation of explorers will discover if we have been able to save the Mediterranean, or if Cousteau's warning came too late.