The whale shark is the world’s largest fish, yet despite its remarkable size remains a mystery to humans. Researchers have yet to confirm where they give birth, for example, or how old they can get (estimates range from 80 to 120 years). They’ve been recorded at depths more than 6,000 feet below the surface, making them the deepest-diving fish but also frustratingly resistant to tracking devices, which can’t stand the pressure. Until 2019, it was anybody’s guess where they mate. That year, scien...