It had been a strange day out on the salt. The wind was hot and sere out of the south, and in the swells you could see the shiny backs of stingrays and the bluish pink air sacs of jellyfish, which meant a storm was probably kicking them in toward shore; then the barometer dropped, the wind died, and the sun looked like a white flame trapped inside the dead water.

It rained for only about five minutes, large, flat drops that struck the water like lead shot, then the sky was clear and hot again and the sweat and humidity ran off your skin like snakes. Far to the south I could see the storm become stationary. Gray clouds were anchored low on the horizon, and right where they met the water there was a white line of surf and an occasional fork of lightning, like silver threads trembling inside the clouds.

While Batist, the black man who worked for me, put out the lines for gafftop catfish, I slipped on my air tanks, flippers, and mask and went over the side, following the anchor rope down through the cone of translucent green light, down to a level of water that was suddenly cold and moving and gray with silt, spinning with yellow blades of seaweed, perhaps alive with sand sharks that could whisk past you with such energy and force that you felt you had been struck by an invisible hand.

The anchor rope was taut and hard when I touched it. Above me I could see the silhouette of my boat's hull wobbling against the light, the bow dipping into the chop against the pull of the anchor. I blew my mask clear and went down ten more feet along the rope, into a barrel of darkness, of swirling silt that had been blackened with oil, into sounds that shouldn't have been there-metal knocking against itself, like a ball peen hammer bouncing idly off an anvil, steel plates grinding across hard-packed sand, perhaps wire cables lifting in the current and lighting on twisted spars.