The entire floor of the lagoon was laid out in squares of greenery: kelp, mosses, and something that looked like giant cabbage. A school of red snappers circled past him, herded by a metal box with a blinking light on the end of one long antenna. Submarines with spindly mechanical arms worked on the ocean floor, thinning the vegetation and darkening the water with chemicals. Two or three dolphins were swimming side by side with human divers, and they seemed to be talking to each other.