When Haven Bay is attacked by pirates in a ship made of rubbish called The Flying Dustman, Alex realizes they are hunting for the Water Dragon’s missing egg. So, he, Zoey and Anil set out to stop the pirates stealing its power, on a treasure hunt that takes them to a secret shipwreck where they must face three monstrous challenges.

The threads of the ocean crowded around Alex, nipping at his skin as if daring him to play with them. He released one of the probes Zoey had invented to monitor the surrounding coastline and it floated in front of him. This close to shore it would drift back to the beach within minutes. Alex needed to summon a wave big enough to drag the probe out of the bay.

He spread his hands in the water and closed his eyes. Pictured a deep well of power inside himself. All he needed was to draw more of it to the surface. Hands clapped onto his shoulders, Zoey and Anil lending their support. It wasn’t quite the same as his link to the Water Dragon, but it was close. The dragon hadn’t given him power. It gave him access to what was already there.

Alex reached for a thread. A thunderous splashing sound made him think he had succeeded. He opened his eyes, expecting to find a towering wave standing at his command. Instead he saw a tremendously round seal barrelling towards him like a runaway boulder.

“No!” he shouted.

The seal knocked Alex off his feet, dunking him under the water. A wave washed them all to shore, Alex coughing and spluttering as the seal licked furiously at his face.

“Loaf!” shouted Zoey. “Get down!”

The seal was one of the first animals to make Haven Bay its home after the water was safe again. A thickly spotted grey back faded to splodgy white over a colossal belly that made the animal almost as wide as he was long.

Zoey, Anil and the otters wrestled with Loaf until he used his stocky flippers to roll off Alex. Stumbling to his feet, Alex opened his mouth to scold the seal. Loaf peered up at him with wide, glistening eyes and twitched his whiskers. He was like an overexcited dog, always ready to play.

“I can’t stay angry at that face,” said Alex.

Loaf gave a yelping bark and coughed up a fish skeleton onto his feet.

The probe had survived the encounter intact and this time they let Anil swim it out to deeper water. It was almost dark by the time they finished, the sky growing an ever-inkier blue.

“Let’s get these things working so I can make it home before my curfew,” said Anil.

Zoey produced a laptop from her waterproof bag and began tapping away at a series of complicated menus onscreen. “They’ve reached the natural currents now,” she said. “Time to fire them the heck up!”

With a flourish, she lifted a single finger high before bringing it down on the keyboard. A steady beeping fuzzed from the speakers.

“The probes check for changes in water quality and temperature. They’ll also alert us to any unexpected arrivals. You know, like maniacal poachers commanding a whole fleet of bad guys, that sort of thing.”

“At least Callis is gone.” Alex gazed out across the bay. Maybe the poacher’s final act was to lie to him, make Alex believe there would be others after him so he would never feel safe. Maybe there was nothing bad out there at all.

The beeping from the laptop became more urgent. Zoey frowned at the screen. Alex felt a heavy anchor sink in the pit of his stomach.

“Is it going to explode?” asked Anil, backing away.

“My inventions don’t do that any more! One of the probes is picking up a strange reading.”

“Fun strange or bad strange?” asked Alex.

Zoey glared at the screen as if it was lying to her and began jabbing keys. “The probe says there’s a big ship approaching the bay at speed. Apparently it’s made from metal, wood and…crisp packets?”

Alex relaxed a little. “It must be broken.”

“Maybe…” Zoey sagged before instantly perking up again. “Wait, another probe is giving the same reading! Tins, plastic bags, glass bottles…this ship is made from more materials than I can count!”

Frenzied splashing from the waterline made them all look up from the laptop. A girl was stumbling onto the beach, sodden clothes plastered to her skin, long strands of green hair sticking to her face. She staggered across the sand towards them, weaving dizzily side-to-side. Loaf and the otters moved in front of Alex to form a protective barrier.

“Are you okay?” he asked. She might have been a tourist who had swum out a little too far and struggled to make it back, except that she was fully dressed in mismatched shabby clothes, including tattered shoes that squelched as she walked.

“You’re Alex Neptune,” the girl said, short of breath, voice pinched by urgency. “You have to run.”

A distant boom rolled across the water behind her. In the fading light, a ship was sailing into the mouth of the bay. Smoke drifted from its side. Snapping in the wind above its tall sails was a black flag, emblazoned with a white symbol Alex didn’t know existed in real life.

The skull and crossbones.

Nobody realized the noise they had heard was a cannon firing until the first shot hit the town.