The North Atlantic water plied by Greta Thunberg in 2019 was around one degree Fahrenheit warmer and 30% more acidic than that which claimed Bas Jan Ader’s life in 1975. The Arctic sea ice has reached record lows, and soon the combination of cold melts and sun-warmed open ocean will negate the currents that carried Bas Jan’s boat to the tip of Ireland. Greta made it. Bas Jan didn’t. It had to be so.