By Sarah Brown (words) & Kashfi Halford (video) RIO DE JANEIRO, Brazil — Just 60 kilometers (37 miles) outside the city of Rio de Janeiro, dozens of Guiana dolphins swim cautiously past the motorboat, cutting through the water’s surface to breathe. Leonardo Flach stands at the bow taking photos to later identify individuals based on their dorsal fins. With a clear sea and surrounding forest-covered mountains, the landscape of Sepetiba Bay is scenic, yet the water is anything but pristine. The Guiana dolphin is “the most common dolphin species in Brazil, but at the same time, one of the most en…