Return of the Ancients mod adds a Gargantuan Leviathan at the edge of the map in the deadzone. It also adds a Juvenile Gargantuan Leviathan that is still 3x bigger than a Reaper or Ghost Leviathan. I was using the console to turn the "fog" on and off, changing the visibility. You can also use the console to change whether or not the creatures can see you.
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#subnautica
#subnautica2
#subnauticamods
#thalassophobia