Today, scientists try to understand them, to go beyond the myths. But stranded or fished creatures offer a poor glimpse into their world. So how can we decipher their underwater secrets without altering their behaviour?
Meet Fred Buyle, a record-breaking freediver who has dedicated his life to this non-intrusive quest. For science, he travels the world to tag or photo-identify large marine creatures that have populated his imaginary world since he was a child.