Chen Hao squatted on the deck, his fingers digging into the hard mud on the sole of his shoe. He pried it off forcefully, the mud shell cracked, and a few pieces fell off. He shook his foot and kicked the last bit of debris into the sea.

"Even the mud in this wretched place seems to be against people."

He stood up and patted his pants. The moment he finished, Nana's voice rang out.

"All supplies have been archived; mission objective achieved."

She stood in front of the locker at the stern, holding the last sealed container. A red light came on, and the latch clicked shut. She placed the container in the lower compartment and closed the lid.

"It is recommended to initiate the return journey process."

Chen Hao opened his mouth, wanting to say "Let's rest a little longer," but he swallowed the words back. He really didn't want to move, but he also didn't want to stay on this ship for another day.

"Okay," he said. "Let's go home."

Susan looked up from her notebook: "Finally leaving?"

"Everything's ready." Carl was tightening the fuel tank cap. "What are we waiting for? The island to sink by itself?"

No one answered. A damp wind blew from behind. The sea was as smooth as glass, and the boat rocked slightly.

Nana walked to the control panel next to the driver's seat and swiped her finger across the screen a few times. "System self-check begins."

Chen Hao walked to the bow of the ship and took out a crumpled piece of paper. It was a rough sketch of the route he had drawn earlier, with a few dots crookedly marked on it, along with arrows and wavy lines.

“I remember we came from the east,” he said, pointing to the map. “We took a big detour because we hit a storm belt.”

"You remember?" Susan leaned closer to look. "I thought you were sleeping the whole time."

“I’m memorizing it even when I’m asleep,” Chen Hao said. “I’m even reciting the direction of ocean currents in my dreams.”

Carl snorted: "Did you dream about how much fresh water was left?"

“Yeah, I did.” Chen Hao rolled his eyes. “I dreamt that I drank the last bottle, and when I woke up I found it was really gone.”

Susan smiled. Nana didn't smile, but after scanning the data, she said, "Freshwater reserves are sufficient; the false alarm has been corrected."

"I told you I wasn't the one who drank it that day!" Chen Hao immediately raised his hand. "It was a system error!"

“You forgot to register after you secretly drank it,” Nana said. “It’s recorded in the behavior log.”

"You still have this?"

"Any behavior that affects the task will be recorded."

I'll format you sooner or later.

“It cannot be executed,” she said. “I am the core control system.”

Chen Hao rolled his eyes and lowered his head to continue studying the sketch. He drew three lines on the paper with a pen.

“The first route is the straightest, but it goes through the remnants of a storm, so it’s not necessarily safe.” He pointed to the second route, “This one is longer, but it goes through a calmer current, so it’s suitable for slow navigation.”

The third line is drawn the lightest and is almost invisible.

“This one… is theoretically the fastest,” he said, “but it requires a westerly wind and precise timing.”

"The risk factor is high," Nana said after reading it. "The current air pressure trend is not conducive to the formation of strong winds, so I suggest giving up."

"I'll just mention it briefly." Chen Hao folded the paper and stuffed it into his pocket. "Whatever you say."

“Then let’s take the second route,” Susan said. “It’s better to play it safe.”

Nana nodded and brought up the navigation model. The screen flashed a few times, generating a route map. She entered the coordinates, calibrated the heading, and checked the remaining fuel.

"The estimated sailing time is thirty-six hours," she said. "There will be no stops along the way."

"Thirty-six hours?" Chen Hao's eyes widened. "Last time I came, it was only twenty hours!"

"We came with the current," Nana said. "The return trip was 70% against the current."

"So we're going to drift back slowly?"

"To be precise, it's moving at a constant speed."

"Could you please stop using such technical terms? It sounds like you're sentencing someone."

Susan laughed. Carl was already inspecting the hull. He walked around the gunwale, squatted down, and tapped on the previously repaired crack.

"The adhesive layer isn't cracked," he said. "The waterproofing is fine."

He tested the engine again and pressed the start button. The machine hummed, ran for a few seconds, and then stabilized.

"It still works," he said, "but the sound is rougher than when it arrived."

“The frequency of use is too high,” Nana said. “I suggest reducing high-speed travel on the return trip.”

"Understood." Carl turned off the power. "We're not going to be race car drivers."

For fuel, they used a type of vegetable oil harvested on the island. This oil wasn't very efficient at burning, but it was good for emergencies. Nana calculated and confirmed that, when mixed with existing fuel, it would be enough to last the entire trip.

“The only problem is the strong smell.” Carl opened the fuel tank and sniffed it. “It smells like waste oil used to fry onions.”

"Don't use food as an analogy," Chen Hao said, covering his nose. "I feel like throwing up just thinking about onions now."

"You threw up?"

“I threw up twice in the cave,” he said. “Once because I felt nauseous, and once because Nana said I had gone the wrong way.”

"You've definitely gone to the wrong place."

"I was almost blinded! It was all light!"

Nana didn't reply. She was organizing the data. The electronic ledger had already been synchronized; now she needed to deal with the paper notes and image files.

Susan opened her notebook and checked each page. Suddenly she stopped writing.

“D5 and D6 are reversed,” she said. “I mixed up the numbers for the blue-winged beetle and the gray beetle.”

"Just fix it." Carl handed over the correction sticker.

She tore off the old labels, rewrote them, and pasted them back on. Then she copied all the sample number lookup tables into a backup copy.

“I can’t afford to make another mistake this time,” she said. “The people at the base won’t tolerate me.”

"They dare say that about you?" Chen Hao leaned against the railing. "You're the only one who dares to touch the glowing fish with your bare hands."

"I didn't touch it! I was just nearby!"

"Anyway, you're braver than me."

"You wouldn't even dare to glance at a dead bird."

"That thing exploded, you know?! It fell apart in mid-air!"

"Alright," Nana interrupted, "the data verification is 90% complete."

Carl transferred all the video footage from the camera to the storage device. There were seventeen videos in total, each with a timestamp and location marker. Nana created an encrypted archive and named it "Complete Record of the First Island Exploration".

"Upload failed," she said. "Signal interrupted."

“That’s normal,” Chen Hao said. “You can’t even use a cell phone here.”

"You can save it locally," Nana said. "You can try reconnecting on your return trip."

She put the equipment into the waterproof case and locked it. Then she went to the control panel and performed a final system check.

"The hull structure is normal," she read aloud. "The propulsion system is ready. Navigation calibration is complete. Supplies are properly sealed. Documents are archived."

She paused, then looked at the three of them.

"Preparations for the return trip are complete."

Chen Hao stood at the bow of the ship, gazing at the distant island silhouette. Darkness was falling, the shadows of the trees forming a black line. He clutched the navigation chart in his hand, his knuckles turning white.

Susan packed her backpack and leaned against the bulkhead to catch her breath. She hadn't sat down to rest in a long time.

Carl patted the engine casing: "This time, we have to get back safely."

Nana stood beside the driver's seat as the light from the optical lens gradually dimmed. She had entered low-power mode, but the monitoring program was still running.

The sea breeze gently rocked the boat. The water reflected the last rays of the sky.

Chen Hao raised his hand and touched the sweat on his neck. He didn't say anything, but simply folded the route map more neatly.

Susan fastened her backpack and glanced up at the dashboard.

Karl tightened the last valve, his fingers still on the handle.

Nana's camera panned slightly, sweeping across everyone on the deck.

Her voice was very soft.

"Everyone, please check your status."