If it's any help (usually) when Leviathan slides across the boat the side he slides to is the side he'll slide back from so.

North > Slide > South
South > Slide > North.

Occasionally he might come from the side too.


As I use headphones I can hear when it's coming sometimes too by keeping my camera still so if its behind me I can hear its going to be on the South-Side so I'll run North.