The build up

"Jimmy has this feeling he's often had here that somebody, or something, is watching him. He breathes in deep, filling his lungs, and dives, his eyes open. The water is surprisingly clear, the tree trunk disappears into the depths. He follows the line down, his gunked-up lungs burning but keeps going. Another big kick. He pulls at the line and it floats up. An anemone, he thinks. A tangle of tenta...