Loki

They would expect him to head for the open sea—he would be safe there, if he got to the sea, even if he would be easy to spot and catch in the river that led from the pool to the bay.
The gods would not expect him to swim back the way eh ahd come. Up the waterfall.
The gods hauled their net along the bottom of the pool.
They were intent upon what was happening in the depths, and so were taken by surprise when a huge silver fish, bigger than any salmon they had ever seen before, leapt over the net with a twist of its tail and began swimming upsteam. The huge salmon swam up the falls, springing up and defying gravity as if it had been thrown upwards into the air.