Recent studies found that elite runners can take in twice as much oxygen as non-runners. And it’s likely that this superhuman ability played a role in breaking the two-hour marathon barrier in 2019. But when it comes to breathing efficiently, not even the best runners can compete with the average fish. What makes fish some of the best breathers on Earth? Dan Kwartler explores the science of gills. Lesson by Dan Kwartler, directed by Denys Spolitak.