Leviathans are ‘large sea creatures’.
http://www.bibleandscience.com/bible/books/genesis/genesis1_leviathan.htm
Behemoths are ‘large land creatures’.
http://www.clarifyingchristianity.com/dinos.shtml
Just a quickie - what is your opinion on the “fire breathing” description of leviathan?
Leviathans are whales....mammals that still exist today.
"Behemoths are large land creatures."
The only reference to a behemoth is in Job 40:15 which is describing a hippopotamus.....mammals that still exist today.