To find the leviathan you need a group of 5 people or more you also need to bribe the guy ontop of the new island and then go to level 6 danger area till it spawns a gate
(ATTENTION) for the buddha users out there. YOU CANNOT CLICK SPAM!! I WASTED HALF OF MY TIME DOING THAT WHEN I FOUGHT LEVI!! then we noticed our boat doesnt have harpoon..😊