Location: Outside U.S.
Date: Winter 2012-2913
How do crocodiles stay afloat while still breathing?
This picture comes from this internet site:
As can be seen in these pictures, a crocodile’s head is higher above the rest of its body so it can hide just under the surface of the water and its nose and eyes can stick up above the water allowing it to breathe and to look around without being seen (unless you are really looking for it). A crocodile has lungs, instead of gills like a fish, so it cannot breathe underwater and it has to stick its nose up in the air to breathe.
The crocodile can float on the water, dive under the water, or maintain its depth. The way it does that is by inflating its lungs changing the amount of water that it pushes out. If it fills its lungs fully with air, it will float because it weighs less than the water it pushes aside when it is in the water. If it reduces the amount of air in its lungs it will sink in the water. Similar to the way a fish inflates and deflates its swim (air) bladder to rise and sink in the water. See the picture below which came from this site:
You can find out more by going to http://www.google.com and type in “crocodile anatomy” and “fish anatomy” and looking for the “wikipedia” sites.
Crocodiles control their buoyancy much like a submarine does. If they wish to float more they can squeeze their liver back, making room to enlarge their lungs!
Thanks for the question. Crocodiles stay afloat because there is a large amount of air in their lungs. This air weighs less than water does and causes the crocodiles to float.
I hope this helps. Please let me know if you have more questions.
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Update: November 2011