Now all that was left was the out-of-air ascent. He ran over the steps in his mind, trying to remember everything Ben had taught him. They’d done it in the pool several times, but because of the shallow depths, it hadn’t been an accurate representation of what it would be like doing it in the ocean. They’d barely had to kick to get to the surface, and the skill was over before it had even begun.

Now Ben knelt, facing Hudson. Then he slashed his hand across his throat and pointed to himself, indicating that he was going to take the role of the diver who was out of air. Hudson gave the okay sign to show that he understood. He took a breath and waited. Ben repeated the out-of-air hand signal, moving his hand horizontally beneath his chin, then bringing his fingertips to his lips and away, imitating the sharing of air.

Hudson reached for his alternate regulator, putting it in his mouth as he simultaneously removed his primary regulator. This he handed to Ben, turning it so that the mouthpiece was facing away from himself. Ben took it and, letting his own regulator fall gently to his side, placed Hudson’s in his mouth.

They were now sharing the air in Hudson’s tank, breathing together. Hudson then moved closer to Ben and took hold of his BC at the waist, so that they were face to face. He gave Ben the okay signal and waited to see it mirrored back at him. Then he pointed surfaceward with his thumb, and they began to swim up.

It was awkward. The regulator hoses seemed to get in the way, and Hudson had a difficult time looking at his computer to monitor their ascent rate while still controlling the release of air from his BC. Also, Ben was kicking hard. Hudson knew it was on purpose; he was simulating what a panicked diver would be most likely to do in this situation.

Hudson let more air out of his BC, slowing them down. He looked at Ben and saw that, behind his mask, his eyes betrayed his amusement. He was enjoying watching Hudson try to do everything at once. Then they were at the surface. Ben handed the regulator back to Hudson and inflated his own BC so that he was bobbing easily.

“Not bad,” he said. “Neither of us has the bends. Good work.”

“Do I pass?” Hudson asked him.

“One more dive,” said Ben. “You have to plan it and lead it. So decide where you want to take me, and we’ll get it done.”

Hudson looked around. “How about over there?” he suggested.

“You’re the dive leader,” said Ben. “I’m just the poor guy who’s following you.”

Hudson gave him the finger. “Oops,” he said, turning his fist so that his thumb was pointing down. “I meant to say I’ll see you on the bottom.”