Hello Akuma
If you play with such methods (exploiting glitch), you can actually get anywhere, even where you currently have no access,
similar to cheating.
Very steep mountain walls or invisible barriers often have the same function as a wall or a locked door.
But because you will destroy the game at this point, we have installed this message.
Please load an older score (before they cross the mountains) and use normal accesses, you will get to this place later during the main quest. To this bay exists a special gate from the land side, which is open exactly then.