When he caught up with the boy, Ahab roughly dislodged Forest’s mask, flooding it with water. He watched as Forest pressed down on the seal and blew through his nose, filling his mask with air again and expelling the water – a standard scuba-instructor test.

Ahab gave him the thumbs up, the signal to surface, and they returned to the top. The sounds above the surface came back all the sharper for having been suppressed – the call of a lone seagull overhead, the snapping of the Ambergris’s mizzen mast sails.

‘Alright,’ said Ahab once the boy surfaced. ‘Now point to every part of your equipment and tell me what it does again.’

‘That was incredible!’ said Forest, spitting out his regulator. ‘That’s amazing!’

‘Yeah,’ said Ahab, eyes crinkling in a smile. ‘Now, tell me about your equipment.’

Forest pointed to the parts. ‘Buoyancy release, weight pockets, spare regulator . . .’

When Ahab was satisfied, he nodded. ‘Now, show me the hand signals.’

Forest reeled them all off perfectly.

Ahab had never had a student like him. He remembered everything Ahab said, word for word.

‘If you’re so good at remembering, show me the five steps for descent again,’ he said. ‘And if you do it properly, we can go for an explore – staying shallow, mind you, and stick close to me. The currents around here are gentle, but that’s no guarantee of anything. When in the ocean or on it, always stay alert.’

‘Okay,’ said Forest around his regulator. He demonstrated the five steps for descent – he signalled, oriented himself by a point of reference, checked his regulator was in place, looked at the time, and then . . . he went under the surface . . . and kept going down.

Cursing, Ahab dived after him, kicking harder when he saw Forest go right past the side of the reef and down, down towards the sand at the bottom. Ahab brought his hand to his nose, equalising the pressure in his ears as he went after him, shafts of light patterning the silt and the kelp.

Forest descended steady and calm. When he reached the sea floor he paused, then sat down flat on his rump. He picked up the sand, looking at it, letting it run through his fingers.

Biting his regulator, Ahab floated beside him, an expert hand on his buoyancy control device, lying flat so his fin kicks wouldn’t stir up the sand.

Forest reached for a piece of kelp, tangling it in his fingers, and held it close to his mask. When he spotted a red weedy seadragon, slowly floating by the edge of the kelp bed, he went still.

Ahab floated closer, looking down at the seadragon, its tendrils and grace, the little fin fluttering like a hummingbird’s wing. Silent and alone, the master of mimicry.

Forest was transfixed, perfectly still until the seadragon softly floated back into the kelp and was gone.