Well written my friend. Whats at the bottom of the bottom though? In the deepest parts of the ocean we have sheets of methane frozen colder then the vacuum of space. On these or around these sheets of ice live creatures that shouldn't exist. Microbes on the sheets even. If something was to evolve to the point of sustaining life in such in-hospitable conditions, who's to say what we still haven't found. As for the Leviathan and the Behemoth, if they are around then they have to have had the longest life ever. For something to exist on that much of a macroscopic scale, the forces that hold them together must be insane. Imagine the Leviathan at the bottom of the see, billions of gallons of water constantly changing pressure as it moves through different depths. The size of something like that would have to have an internal structure akin to titanium to stop itself from collapsing in on itself.