The fish is thrashing about now, wounded, half-blinded, and confused by all these colors and clouds and strange things happening all at once. It has never dealt with intelligent prey before. The most it can do is try to turn around and lunge at whatever moved closest to it.

Which was good news for Kassan as he caught up to the others, since unlike them, he had zero desire to get close to the damn thing. Nah, if that thing wanted something to hit, he'll give it something. Now, where did that boulder get- ah, here we are; on the lakebed. It was a bit chipped from its first visit to the fish's mouth, but still more than serviceable as a bludgeon. He lifts it up with Psychic and pushes it through the water towards Mr. Fishy, hoping to sandwich their target between the boulder and the rock wall.

Everyone else might want to move out of the way.