“Loco,” Jack cried, climbing to the cave. “Tom needs help.”

“Dog?” Loco screeched.

“I said, ‘Tom needs help!’”

Tom rose in the water and crashed down on the surface again.

“Just calm down and try to untangle yourself,” Jack called out. “Loco, I have to go out and see if I can do anything.”

He grabbed his mask and fins. “Tom will kill himself on the coral if he keeps this up. He got us to the island. We have to help him if we can.”

Jack swung out on the rope and dropped into the sea. He yanked his fins on and kicked across the bay.

The channel loomed in front of him, funneling four-foot swells. Jack put his snorkel in and kicked. A wave picked him up and threw him back. He kicked harder, inching forward as the sea pushed him dangerously close to the coral wall.

He got through to the open sea, and a wave broke over Jack’s head. His snorkel filled with water. Jack ripped it out of his mouth. Another wave broke and pushed him under. He was drowning.

Jack’s fins brushed something solid, and he was heaved out of the sea. Smooth, spotted flesh stretched out underneath him.

Tom.

Jack lay on Tom’s back, coughing out seawater. He caught his breath and pulled his mask down around his neck. The net sticking to Tom had looped around the shark’s dorsal fin.

Jack patted Tom’s back. “Now, Tom, I’m just going to get that net off your fin. Do not thrash us onto the reef or anything, okay?”

He inched back toward Tom’s dorsal fin.

“Good, Tom,” Jack said. “Just hold steady. Exactly like you’re doing.”

The cause of Tom’s problem looked like an old and rotting fishing net with bits of trash tangled in it. Jack grabbed the edge of the net and tugged. Stuck.

“Okay, Tom, I need to get a little closer.”

Jack crouched on the whale’s back as they rode up and down the swells.

There. There was the reason Tom couldn’t get loose. A hole in the net had snagged the tip of Tom’s fin. Jack tugged the net upward until it came loose, then pulled it all the way off. The net slipped into the sea and floated away with the current.

“We did it, Tom,” he cried. “It’s off! Now stay away from that net so you don’t get caught in it again.” Jack lay on the shark’s back, looking toward its massive head. Tom’s smooth flesh felt cold on his skin. He patted the shark and said, “Good job, Tom.”

Tom arched his back. Jack slid toward Tom’s head.

“Hey! Cut that out!”

Tom’s head disappeared underwater. The shark was diving. Jack jumped off and kicked away. Tom’s dorsal fin submerged; his tail fin followed. He was gone.

Jack twisted around. He was farther from land than he had realized, and the current was pulling him past the channel. He put on his mask and snorkel and began to kick. The sea beneath him looked bottomless. Tom had become a dark shadow, swimming deeper and deeper.

Jack fought against the current, using the long, powerful kicks he had practiced inside the reef. It felt as if he were hardly getting anywhere. If he stopped kicking for a moment, the powerful sea swept him backward.

Kick by kick, he finally neared the channel. A wave pushed him forward, then pulled him back again. Another wave tossed him surging into the bay.

Jack crawled up on the beach, breathing hard, the warmth of the sand sinking into his body.

Back in the cave, Jack lay on the tarp, exhausted. “I know what you’re thinking, Loco. I shouldn’t have done it.”

“Whatever.”

“In the end, though, it worked out. There were times I was worried. I won’t lie about that. And I don’t know why Tom dived down and left me by myself. That didn’t seem very grateful.” Jack paused. “I suppose I’ll never really know what Tom was thinking. All I can do is add what he did to the rules of engagement for whale sharks. Rule: no matter what else is going on, a whale shark might suddenly decide to dive.”

“Whatever.”

Jack twisted around and looked at Loco. “You know, you should really stop being so cynical.”

The next morning, Jack ran to the top of the ridge and scanned the sea.

Tom looked good as new. He drifted along the reef, his mouth wide open, eating his plankton breakfast.

A white outboard sped around the far tip of the island.

“Hey,” he cried. “Look up! You have to look up! I’m right here! Again!”

The boat slowed to a drift outside of the channel.

Jack’s dad scanned the beach with binoculars. His mom stood at the back of the boat, shooting off signal flares. Bursts of orangey-red light spattered the sky like bucketfuls of paint.

“What are you doing?” Jack shouted. “Look up!”

Jack grabbed a heavy rock and tried to throw it into the sea. It rolled down into the trees.

His mom grabbed his dad’s arm. She pointed to the sky, then sent up another flare. They watched it explode and fizzle out, then high-fived each other.

“Don’t get distracted!” Jack said. “Look up! Up!”

Arms pumping, Jack sprinted down the slope to the beach, weaving around stands of bamboo.

He burst out from the trees and jumped up and down on the sand. “Now, seriously!” he yelled. “You can’t miss me this time!”

Jack’s dad looked toward the island. His dad grabbed his mom’s arm and pointed to Jack.

“Hold on, Son. Help is on the way!” he shouted. The boat headed toward land at full throttle.

“The channel!” Jack yelled. “It’s over there. To the left! To the left!”

“Yes, we see you, Jack,” his dad shouted. “We’re not idiots!”

The boat rode up onto the reef with a splintering sound. Jack’s parents were thrown to the deck. They staggered up, and his mom brushed the hair off her face.

Water flooded the stern. The spot where the engine had been was now a gaping hole.

“Bit of a technical problem,” his dad called.

Jack stood motionless. His parents had wrecked the boat.