In great haste, a swarm of Endless Swordfish was headed in Han Sen's direction. They didn't come for him, but simply sped past him as if they were attempting to get away from something that lay in the direction Han Sen was traveling.
Han Sen understood their behavior, acknowledging that they were fleeing some unseen menace on the horizon. They weren't there to cause trouble.
After peering into the distance all around him, Han Sen finally saw it: a shadow, accompanied by the sounds of disturbed water. When the Endless Swordfish passed by the Fish King above, the sound of restless waters became louder than ever. And that was when Han Sen saw it clearly.