The fish did not hear the sound, but rather registered the sharp and jerky impulses emitted by the kicks. They were signals, faint but true, and the fish locked on them, homing. It rose, slowly at first, then gaining speed as the signals grew stronger. The boy stopped for a moment to rest. The signals ceased. The fish slowed, turning its head from side to side, trying to recover them. The boy lay perfectly still, and the fish passed beneath him, skimming the sandy bottom, Again it turned.