When looking into the reproductive habits of Kronosaurus queenslandicus there is a limitation on the direct evidence.  While it is a not certain fact, it is commonly thought that Kronosaurus was vivaporous, which means to give birth to live young  (Renneboog, 2011).  This is thought to be true due to the shear size of Kronosaurus, which would not allow it to easily beach itself to lay eggs.  Modern organisms that are also vivaporous include dolphins, sharks, and whales.

Clearly there is no video evidence of Kronsaurus giving birth,  but if you are interested in what it might have been like, check out this amazing link of a dolphin giving birth!

 This is an idea of what it would have been like for Kronosaurus, but on a much smaller scale.