The circulatory system of a crocodile is composed a four chamber heart which is similar to that of mammals , and birds. He has about the same kind of pumping blood throughout the body where needed. It also helps vital nutrients get to all the vital muscles of the animal but allows growth to occur. The crocodile has some unique features which allow it to keep it's body submerged underwater for almost two hours. This animals has a closed circulatory with veins and arties like normal mammals and has about the same system for human go down for a dive and then back up for air.The change in blood circulation with its aortas allow maximum time under water, its use of its body temperature , and the controlled blood allows this mighty be the predator and animals we all fear yet admire it.
http://www.fountainmagazine.com/Issue/detail/extraordinary-blood-circulation-in-crocodiles-march-april-2013
As shown in the picture the crocodile has the same circulatory as birds and mammals with two aortas and two ventricles making sure that the croc always has enough oxygen and it still allows them to live its normal life and carry out it's normal deeds.