Beginner's Cave Diving Course

After Su Ming and his group finished dressing, they entered the deep water area.

He felt a warm sensation as his body was completely submerged in the water.

Su Ming glanced at his wristwatch and noticed that the water temperature had reached 28 degrees Celsius.

"That's normal," a diving expert explained. "You're currently at a volcano, where geothermal activity is present."

"That's good," Su Ming said. "At least it reduces the risk of hypothermia."

He submerged his face in the water to test the full-face mask, confirming that no air bubbles escaped from the edges and no water seeped inside.

Su Ming tried taking a breath.

The respirator made a slight mechanical sound. There was more resistance than when breathing on land, but there was no suffocating feeling of not being able to breathe as I had imagined.

He leaned forward, water flowing over his entire face mask, leaving shimmering ripples at the edge of his vision.

Su Ming subconsciously swung his arms, trying to maintain his balance.

"Don't paddle," the expert's voice came through the communicator. "Relax, use your flippers. Keep your body as horizontal as possible."

Su Ming did as instructed, using his flippers to push off the water, and his body immediately slid forward a short distance. Resistance was everywhere; every movement was slowed down by the water flow, and if he exerted too much force, his body would tilt to the other side.

After several rounds of back and forth, Su Ming gradually got the hang of it.

By controlling your breathing and reducing unnecessary movements, your body can remain suspended stably in the water.

****

"Communication test," Vios said.

"Clear," Su Ming replied.

The advantage of a full-face mask is that it allows for uninterrupted voice communication.

On the other hand, Simina made the fastest learning progress, after all, she had actually spent two months here. After becoming familiar with how to use the technology equipment, she was soon able to easily dive to depths of tens of meters.

The girl's breathing and heart rate were very steady, clearly indicating good adaptability, far surpassing that of the two newcomers, Su Ming and Yise.

"Don't stay in deep water for too long to avoid decompression problems," the expert advised her.

"Understood," Simina replied.

There are many courses. The closed-circuit respirators they carry, also known as CCR, use a ternary gas system of oxygen, nitrogen, and helium. The proportion of these three gases needs to be changed as the diving depth changes.

The system will adjust automatically, but all three people need to understand the underlying principles.

Simina was deeply impressed by this extremely detailed knowledge.

"If we had known these concepts back then, we wouldn't have taken so many detours and wasted so much time."

Su Ming was somewhat curious.

How did you manage to do that back then?

"First, we chose to operate during the dry season," Simina explained.

"The water level wasn't this high at that time, and there were multiple air chambers in the passage, with rest areas every one or two kilometers, which greatly reduced the difficulty."

"Secondly, there's human resources. I brought two high-ranking royal knights with me, and I also hired a squad of half-servals to assist us."

Finally, there's the power of money.

"Including all the alchemical equipment and magical materials, I spent a total of 60,000 gold coins to achieve my goal."

Su Ming sighed. "Researching this kind of thing isn't something poor people can do."

"It's not something an ordinary person can handle either," Simina readily admitted. "I'm the most extravagant of all the children of the Pearl Duchy family; I spend money even more recklessly than those spoiled brats."

"Your book is so popular, you must be making a lot of royalties, right?" Yise asked.

"We've given it all up, and it's still not enough," Simina sighed.

"That's enough to burn through money."

****

The three began to increase their diving depth, and Zijin also activated the little bone dragon.

She tested the underwater movement spell attached to the bone dragon. The little bone dragon flapped its wings, pushed aside the water, and swam back and forth around the group.

After testing for a while, Zijin was not satisfied and asked Jinxiu to make some changes on the spot.

"Your Scholar Bay Owl, is truly astounding when it comes to spending money," Simina said. "Back when she was researching 'reverse object regression,' she spent 300,000 gold coins in just two months."

"Reverse Object Reversal" is a spell that can restore an object to its original form, but the restored object will be destroyed after the spell's effect ends.

In the process of reconstructing the new divine language, Zijin used this spell extensively. When studying the Rift Clan ruins, Chloe also relied heavily on this technology for backtracking. Su Ming gasped and turned to the little bone dragon.

"Just one spell, and it costs this much?"

"Don't listen to Simina's nonsense." Zijin activated the sound spell on the bone dragon, her tone extremely dissatisfied. "I only spent 20,000 gold coins back then."

"Ah!" Simina exclaimed in surprise, "Did I remember Zero wrong?"

"No," Chloe interjected from the other end of the communication. "There are 280,000 gold coins; it's compensation paid by Chestnut Owl."

"So what did you do?" Su Ming asked, puzzled.

Zijin pouted.

"During the experiment, the Supreme Knowledge Association was accidentally destroyed..."

Su Ming didn't understand.

"What did you dismantle in the Supreme Knowledge Society?"

Zijin glanced at him.

Su Ming suddenly understood. (The last line appears to be a string of characters and doesn't translate directly.)

"Wait a minute, you don't mean you're referring to dismantling the Supreme Knowledge Association, do you?"

Zijin snorted.

"When you have a hammer in your hand, everything will look like a nail."

She argued.

Su Ming couldn't help but complain.

"That nail is way too big for you!"

"Since then, the Supreme Knowledge Association has stopped holding its annual meeting at its headquarters," Chloe added.

****

Afterwards, everyone learned how to deal with water getting into a full-face mask.

Su Ming felt that this was very different from what he remembered about diving.

Think about those seaside resorts where tourists, after receiving simple training, can put on a scuba suit, go into the water with an instructor, take photos, and check in. Even older tourists can do it without any problem. But now, using these things is much more complicated.

"There's no way around it, the needs are different," the expert team explained. "The equipment we've configured for you is naturally different."

"Be grateful," Jin Rongjia said, "It was I who stopped them from using hydrogen diving."

"What's wrong with hydrogen?" Su Ming, puzzled.

"We'll mix hydrogen and oxygen to make a breathing gas for you," Jin Rongjia said.

"Can that thing breathe?" Su Ming asked in surprise.

"Hydrogen has many benefits," an expert recommended. "It has the lowest breathing resistance, almost no anesthetic effect, and can greatly reduce the difficulty of treatment."

"Then a spark or a static electricity crackle, and it will explode with a bang," Jin Rongjia added mercilessly.

"That was really exciting," Su Ming said.

An expert raised his hand.

"It wasn't completely useless this time."

"Your rescue gas cylinders use a mixture of hydrogen and oxygen." Su Ming was startled.

Why use that?

"Just in case," the expert said. "You'll understand when the time comes if it really comes."

****

Thus, under the guidance of the expert team, Su Ming and his group violated almost all safety rules to conduct a beginner's tutorial for this most challenging diving activity.

The Lingyu is also encountering some problems.

A landslide occurred in the lava tunnel, with several large boulders blocking the center of the tunnel.

Although the passage was not a major problem, the expert group decided to blow up the rocks blocking the road.

In their words, there's no need to give newbies like Su Ming and Yise the hard way.

"Won't blasting make the collapse worse?" Su Ming asked.

"Therefore, internal demolition is necessary," the expert team replied.

The slug deployed its mechanical hooks, located a nearby anchor point, and secured the machine firmly. Then, a drill bit extended from the front of the machine, pressed against the rock, and began drilling.

Although the rock was quite hard, it was still cut open as quickly as tofu by the high-speed drilling equipment.

"Your drill bit is incredibly powerful," Su Ming said.

The power of the drill bit itself is not the key issue; the real problem lies in the power supply.

The current umbilical cable is over one kilometer long. Although the submersible has its own batteries, they must be continuously replenished by a generator at the rear.

Otherwise, the battery life would be extremely poor.

However, in order to reduce weight, the umbilical cord cable cannot be made too thick.

"A 35 kV medium-voltage DC power supply system." Ji Su smiled. "The technology from aircraft carriers has been used in a tiny submarine. Be content."

A huge capacitance will form between the cable and the water, resulting in severe loss of alternating current.

This problem does not exist in direct current (DC) transmission.

High voltage, on the other hand, will significantly reduce the current.

The resulting insulation requirements were addressed by alchemical materials from the magical side. These materials, which were originally of little use in Teya, had dielectric strength that always made the engineers on the technological side's eyes light up.

****

After scanning, the expert team identified several blasting points. The "Lingyu" submersible drilled holes in the rocks one by one and inserted the explosive rods and detonators into the holes.

The Lingyu's thrusters reversed, and it reversed to a safe distance.

The re-inspection was successful; detonation permission has been issued.

The next moment, a flash of light appeared, and the entire passageway trembled slightly.

A muffled "thump" sound, suppressed by the water, suddenly rang out.

Cracks spread outwards from the point of explosion in a spiderweb pattern within milliseconds, and the rock mass disintegrated.

The shock wave expanded outward in a spherical shape, carrying rock fragments to form a fog-like cloud, which then quickly froze and even collapsed inward.

Due to the obstruction of the water flow, the gravel did not scatter but instead collapsed downwards, carrying with it mud and sand. The resulting sediment, like a dust storm, quickly engulfed the underwater camera's field of vision.

All that remained on the screen was a swirling gray-white, with rock fragments occasionally striking the outer shell of the machine, producing a soft, tapping sound.

Nearly thirty seconds later, the silt began to settle. The image gradually became clear, revealing that the upper section of the passage had been cleared, while the bottom was piled with jagged, uneven stones.

A few wisps of fine sand drifted up from the cracks, like a sigh after turmoil.

The wrecked fish successfully completed its mission, dragging its cable as it flew overhead.

"This explosive has very poor performance."

Su Ming has also learned a lot more about this, after all, they're blowing things up all the time now, and on a huge scale.

The shockwave from the explosion dissipated quickly and did not damage the cave walls at all.

"We used low-velocity explosives," the engineering expert explained.

Water is incompressible, and the peak pressure generated by an explosion can be dozens of times that of air.

However, the degradation is also rapid.

In particular, the presence of static pressure in the water causes the high pressure to compress the bubbles generated by the explosion, shortening the oscillation period.

The low-intensity explosives chosen by the experts only covered the obstruction, with the excess impact energy rapidly attenuating and dissipating in the water.

**** When the cable carried by the slug reached its end, it disconnected the umbilical cable, fixed the connector to the cave wall, and then returned to Earth using its own batteries.

Vioas attached a new cable to it, and the Mackerel then returned the way it came, connecting the old and new umbilical cables before continuing its exploration.

After practicing for several hours, Su Ming and Yise were exhausted and dragged their heavy equipment to the shallow water to rest.

Simina, who is still in the recovery period, has already successfully descended to fifty meters.

She was still hungry and wanted more, so she finally surfaced.

The day passed just like that.

Because of the intense activity, Su Ming fell into a deep sleep right after dinner.

The next day, everything continued as usual.

The Slug completed its exploration of the passage. It searched back and forth between the branches, successfully located the upstream air chamber area described by Simina, and laid cables there.

Su Ming looked through the 3D map and felt it was much simpler than the "Death Mine" dungeon map in a certain game.

"The design is very simple," he commented.

"Most lava tubes are like this," the expert team said. "When you go back to Earth, go explore some caves, and you'll see what 'hell difficulty' really means."

The total length of this passage is 7.8 kilometers, which is within the range of the Lingyu (a type of slug).

Vioas packed the supplies into neutral buoyancy tanks, which were then transported there by the Mackerel.

Upon arrival at its destination, the Lingyu (a type of scuba tank) releases its buoyancy tank, recharges, and returns.

And so it went back and forth.

Su Ming and Yise gradually became able to dive freely to the bottom of the pit fifty meters deep, learning to deal with unexpected situations and clear obstacles from the equipment underwater.

As for Simina, let's not even talk about this mermaid.

The expert panel reluctantly checked the "qualified" boxes after each assessment.

Two days of practice was the minimum that the expert team could accept.

****

On the third day, everyone packed their belongings.

"Take good care of the house." Su Ming patted Vioas on the shoulder. "Good luck, brother-in-law!" Vioas replied.

The three of them entered the water one by one and slowly descended to the bottom of the pit.

Su Ming turned on his headlamp.

The closed-loop device allows for almost no bubble escape and provides excellent visibility.

But the bright beam of light pierced the underwater surface, illuminating only a limited area; beyond that lay a thick darkness.

"Communication test," Vios's voice came through.

"Number One is normal," Su Ming said.

"Number two is normal," Simina said.

"Number three is normal," Yise said.

"Depth 57 meters, oxygen partial pressure 1.26, nitrogen partial pressure 2.22," the expert team at the rear said. "You have two sets of sensors, but if the sensation is incorrect, remember to investigate the problem."

"Receive!"

The three men secured themselves together with the safety rope. The Lingyu (a type of submarine) led the way, and the three men lay flat and activated the diving propulsion system (DPV).

The thruster churned the water, and the group was pulled into the lava pipe by a steady force.

Su Ming used a CCR closed-loop system for this operation. The exhaled air was recovered and filtered out of the carbon dioxide by an adsorbent, making it much more efficient than an open-loop scuba system.

Under the same load, CCR can be maintained for more than four times longer.

The disadvantages are that the operation and usage process is complex and the fault tolerance is low.

Another advantage is that without air bubbles, the sediment is less likely to be disturbed. Otherwise, in enclosed caves, the phenomenon of "black water" that can instantly reduce visibility to zero could occur.

The lava passage has a flat bottom and a semi-circular top. Some of the rock walls are so smooth they are almost reflective, while others are covered with honeycomb-like pores and sharp protrusions.

The guide cable is fixed to one side of the tunnel wall, and there is a faint light marker at regular intervals.

Like a signpost in an abyss. The light behind gradually shrinks, and a new signpost emerges from the darkness ahead.

The beam of light from the headlamp was like a long white cone piercing the darkness, and particles suspended in the water drifted past my eyes.

The distorted flow lines on the cave wall receded under the light, and occasionally a few small fish could be seen, which, startled by the light, quickly scurried away along the crevices in the rock.

The surroundings became extremely monotonous. Dark cave walls surrounded him, the constant hum of the thrusters filled his ears, and even his own breathing became abnormally clear.

****

After setting off, the group left the coverage area of the communication relay signal and temporarily lost contact with the rear.

However, upon reaching each node, Simina would connect to the pre-installed interface on the cable to report back.

"Horizontal travel distance: 0.8 kilometers; depth: 45 meters; visibility: good."

"All data are normal."

"Received!" the expert team at the rear replied happily.

The passage was mostly straight with gentle turns, and apart from checking in every now and then to let everyone know they were safe, there was almost nothing for anyone to do.

"Compared to last time, this is like playing in a swimming pool," Simina exclaimed.

"I think this is even more boring than the swimming pool," Su Ming complained.

Fifty-three minutes later, the situation ahead changed.

A beam of silver light hung overhead, Light Cut fragmented spots of light. "We've reached the air chamber!" Simina exclaimed. "Depth to zero."

With a few splashes, the three of them emerged from the water.

This is a sizable natural cave, with its highest point reaching nearly ten meters.

The headlamp swept across the cave ceiling, which was covered with dark red lava stalactites. A few condensed water droplets fell, creating ripples on the surface of the water.

"The oxygen content is only 18%, and the carbon dioxide concentration is a bit high," Simina glanced at the data. "It's within tolerable limits."

The three climbed out of the water one after another and removed their breathing masks.

Su Ming had just taken a breath when he felt a tightness in his chest.

The air was warm and humid, with a strong smell of damp rock mixed with a faint sulfur smell, offering no hint of freshness.

Su Ming couldn't help but take deeper breaths, his heartbeat gradually quickening.

Yise's situation was similar to his; as soon as he took off his mask, he frowned and took a few breaths.

Simina took out the water harp, and a blue light enveloped the three of them.

"Gentle Breeze Barrier!" A very faint cyan light screen unfolded around the three of them. The surrounding air was filtered, and the oppressive, suffocating feeling quickly lessened.

"Don't move too violently," Simina cautioned. "This barrier is very fragile."

"Understood."

****

As you walk uphill, you'll find several flat, man-made rocky areas.

There were many wooden crates scattered around, their surfaces covered with large patches of grayish-white mold.

"These are supplies we left behind two years ago," Simina said.

She searched through the items and realized that consumables such as food were definitely unusable.

But some daily necessities are fine; cups and such can be washed.

"A tent?" Yise asked in surprise.

She checked it and saw that it also had mold spots, but it was a washable material.

"Yes, we were stuck at this location for over a month," Simina said. The three of them dragged the floating cargo container ashore, set up communication equipment, and connected cables.

"Arrived safely!" Simina reported to the rear.

"Yes!" Viaas exclaimed joyfully, "The mission is mostly complete, only the last few hundred meters remain."

"You're overthinking it," the expert team at the rear laughed.

"Tutorial complete, cave diving officially begins!"