Axolotls are in the brink of extinction because of water pollution and introduction of non-native species in their habitats. They are endemic to lakes in Mexico, although people around the world have them as pets and many are research subjects. Currently, scientist are interested on their ability to regenerate limbs. A professor in Chicago has genetically engineered glowing axolotls (not sure why).
Anyway, you can see how axolotls swim and how their gills sway in the water. BTW they have gills and lungs!