The arapaima is a giant freshwater fish. Exactly how large it can grow is uncertain, but reaching three meters in length is not unusual — and there are many stories of even bigger specimens.
Fossils of arapaima dating back 150 million years have been discovered, suggesting that the species lived alongside the dinosaurs. For this reason, it is often described as a “living fossil.”
The arapaima has developed a swim bladder that functions like a lung. It lives in the rivers of the Amazon Basin, where oxygen levels in the water can be very low. When oxygen is scarce, the arapaima surfaces to gulp air.