Siblings and underwater adventurers Céline and Fabien Cousteau carry on their family's legacy (they are grandchildren of famous oceanographer Jacques-Yves Cousteau) by setting out to uncover tales from the sea that remain shrouded in mystery. Céline and Fabien use cutting-edge technology, their diving expertise and a thirst for knowledge and adventure to seek out the answers to some of the most popular and perplexing mysteries, including shipwrecks, strange scientific occurrences and natural anomalies, all beneath the sea.