Instead of Border Guards stationed at the border wall, there were Spirit Beasts.
Eagle-eyed Tigers. Basically a beast with the body of a tiger, and the colors and astute eyesight of an eagle. They were placed there for a reason, capable of seeing through the darkness of the night for any approaching threats.
However, shadows worked as well underwater as above the surface. The ocean was a dark, dark place. Even darker than the surface.
Swimming through the Shadows was difficult. When he dove into the Sea of Darkness, he had to close his eyes and maneuver entirely through his Shadow Sense.
Liam bordered the cliff.
Behind him were the hundreds of Shadows.
[Let me go in first,] Liam transmitted to Krel, who nodded after a short pause of reluctance. [I'll tell you when to come.]
Mental waves could pass through underwater just as they did through air. Albeit, it made them wobbly and unstable.