Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page Visit Our Archives Ask A Question How To Ask A Question Question of the Week NEWTON Teachers Our Expert Scientists Volunteer at NEWTON! Referencing NEWTON Frequently Asked Questions About Ask A Scientist About NEWTON Education At Argonne Crocodile Buoyancy

Name: Prathyoosh
Status: student
Grade: 4-5
Location: Outside U.S.
Country: India
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 and type in “crocodile anatomy” and “fish anatomy” and looking for the “wikipedia” sites.

Sincere regards, Mike Stewart

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!

Grace Fields

Hi Prathyoosh,

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. Thanks Jeff

Click here to return to the Zoology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 223
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: November 2011
Weclome To Newton

Argonne National Laboratory