Although the walls were slippery, Yu Fei could completely control his sliding speed by spreading his legs and kicking on the walls on both sides. The nylon rope was at hand to ensure that he could stop at any time.

Yu Fei brought two waterproof lights, one worn on the top of his head and one carried in his backpack. When gliding, Yu Fei listened intently to what was going on below and raised his head to let the light illuminate the direction of travel.

Finally, when the sound of water became clearer and clearer, he reached out and grabbed the nylon rope, used his feet to push off the moss on the stone wall, and his speed quickly slowed down.

call……

Finally, he stopped just before encountering the water.

The water illuminated by the light was clear and transparent, but deep down it was dark and nothing could be seen.

Yu Fei licked the corner of his mouth. This was a journey that he could not go back the same way. To be honest, the feeling of despair last time made him a little scared when he thought about it now.

As he gained more and more knowledge, Yu Fei deeply felt that the sentence was correct. Don't challenge the majesty of nature. When nature truly shows its power, you cannot bear it.

Looking at the turbulent water below, Yu Fei calmed down for a moment, put on the oxygen mask on his face, and his underwater eyes. Finally, he checked the equipment on his body. After making sure that everything was reliable, he took out the rope specially used for it.

The pulley on the boat was fastened and jumped directly into the water.

The underground water was very cold. After entering the water, Yu Fei felt a chill that quickly penetrated the diving suit, but he could still bear the chill.

Yu Fei did not tighten the pulley he was holding in his hand, but allowed himself to move forward along the current, so that he could enter a position similar to the dam gate where he had been rushed before.

However, Yu Fei didn't want to compete with the stone to see who was harder. After estimating that the distance was about the same, he slowly tightened the pulley, slowed down his speed, and allowed his body to slowly move forward along the current.

Because he wore underwater vision glasses and a flashlight this time, he finally saw the surrounding situation clearly. This was a real natural underground river. The surrounding stone walls were uneven, and some even looked very sharp.

If an average person is driven by the current and crashes into it at a very fast speed, there is a high chance of death or fractures on the spot. Yu Fei is very lucky that he was lucky enough not to be hit last time, otherwise even he would have choked on the saliva.

Choking to death here.

The water flow suddenly slowed down a bit, and Yu Fei opened his eyes slightly, because he knew that the place similar to the gate had arrived, so the speed of the water flow slowed down.

The nylon rope prepared by Ma Laodao is very strong and long enough, so it is not over yet. I can use the pulley to control my speed.

As long as you follow the water flow, you can reach the gate. Yu Fei carefully checked the surrounding situation, and did not take it lightly just because it was underground. Some animals can also survive underground, and the animals that can survive in this place all have certain characteristics.

With his unique ability, it is not impossible to be extremely aggressive.

Fortunately, Yu Fei hasn't found any creatures in the water for the time being, and he didn't find any creatures last time he entered.

Finally, he followed the water to the gate, and a strong suction force appeared. For fear of breaking the rope, Yu Fei hurriedly relaxed the pulley in his hand, and was instantly sucked in.

The inside of the gate was not as smooth and straight as imagined. It seemed to have appeared naturally. Therefore, after entering, Yu Fei tried his best to control his speed and observe the surroundings. However, even in the rapid water, it was difficult to see anything clearly.

Boom boom boom...

Waves of dull sounds came, and Yu Fei grinned, because this meant that he was about to go out. That was the sound that the water in the gate would make before entering that section of the artificial river embankment. The water flow was released, so the sound it made was

sound.

Just as he felt that he had left the gate, Yu Fei hurriedly moved upstream. Within ten seconds, he surfaced.

"call!"

Yu Fei opened the smoke mask and took a deep breath.

Cough cough cough…

As soon as he took a breath into his body, Yu Fei immediately coughed violently and quickly put the oxygen mask on his face because he found that there was an unpleasant smell in the air and the oxygen was very thin.

Then Yu Fei discovered another problem. The length of the nylon rope finally came to an end, and the buckle on his body and the pulley in his hand were empty.

In such currents, it is very difficult to swim back, and it makes no sense. It is impossible to swim back to the ground against the current.

Yu Fei hurriedly turned around and looked around. With the help of the waterproof light this time, he did not appear to be blinded.

Yu Fei quickly swam towards the embankment of the artificial river. This part of the artificial river was very short. If he couldn't reach the shore before being washed downstream by the water, he would have no choice but to find an exit and leave.

After swimming hard in the water for more than a minute, Yu Fei finally reached the shore. The end of the artificial river embankment was just a few meters away. If he had been slower for a few seconds, he would not have been able to get ashore.

Climbing up to the shore, Yu Fei lay directly on the stone embankment with his back facing the sky. He couldn't help but sigh in his heart. He was really lucky last time. First, he didn't crash to death on the stone, and then he rushed out just in time.

On the edge of the river embankment, if it hadn't been for this series of luck, even he would have drowned in the cold water last time.

However, there is a very strange situation. Although the air here is almost isolated from the outside world, the last time I came here, the oxygen here was definitely enough to breathe. Now it is so thin. Yu Fei is very puzzled. What is the reason?

Oxygen is consumed.

After resting for more than ten seconds, Yu Fei immediately got up. If Ma Laodao was still here, it was most likely that he was inside the cave he found. Although it collapsed, there was at least a distance enough for him to stay.

While walking, he used the waterproof lamp prepared by Malao Road to observe the surroundings carefully again. Yu Fei finally confirmed that he had really overestimated the ancients. This so-called artificial river embankment was carved out of the original stone faults.

That's all, otherwise modern people wouldn't be able to do this kind of underground engineering, let alone the ancients.

But this is already very impressive. Yu Fei thought before that this section of the river was purely artificially created, which would be really amazing.

Walking quickly to the entrance of the passage, Yu Fei hurriedly looked inside. It didn't matter if he didn't look, but he was shocked when he saw it, because Ma Laodao was lying naked inside, and everything he brought in was thrown aside.

Yu Fei hurriedly went over and took a breath. Although he was not dead, he was almost alive. His breathing was very weak and his heartbeat was extremely slow. It seemed that it was caused by severe hypoxia.

The oxygen in his own diving equipment had been completely exhausted. Yu Fei quickly put his oxygen mask on Malodao and passed some spiritual energy to Malodao. Malodao's breathing and heartbeat finally began to slowly recover.

Yu Fei then observed his surroundings, and then he saw a pile of burned solid fuel on the ground, with Ma Laodao's clothes beside it. Yu Fei suddenly laughed angrily.

It is estimated that when Ma Laodao went through all kinds of hardships to get here, the oxygen was basically exhausted because it took too long.

In addition, he was old and frail, and his clothes were soaked. It would be too much for his body to wear them, so he planned to light a fire to dry the clothes.

Little did he know that this was a closed environment with limited oxygen. When the oxygen content gradually decreased, he himself fainted without knowing it.

This is really a case of fainting before leaving the army, and getting sick for nothing. Even if Ma Laodao goes out this time, if he doesn't care, it will probably take a long time for the body to recover. After all, let alone the cold, the brain will take a long time.

Without oxygen, your brain will not be used well without turning into a fool.

Yu Fei stood up and walked around, and found that the environment here had not changed much. He walked over to look for the artificially carved patterns he saw last time, but when he walked to the original location, he found that the patterns on the wall were gone.

Yu Fei was shocked and hurriedly went up to take a closer look. He immediately discovered that it had been artificially rubbed away with something. If he hadn't known that there was a pattern here before, he wouldn't have been able to see it at all.

It was obvious that the carved pattern was found by Ma Laodao, but he destroyed it after reading it himself. His intentions are difficult to guess.

After walking around for a while, Yu Fei found nothing, so he was ready to leave with Ma Laodao. Yu Fei believed that even if he saw the pattern, he might not be able to decipher it.

So Yu Fei was not going to wake him up, otherwise it would be like pointing out the way out for him. If he remembered the pattern, he would be able to figure out the mystery and know that it was a map.

With this old guy's virtuous character of not being afraid of death, he would not come down every day to do what Yu Old Man Moved Mountains and remove the collapsed stones in the passage.

After sorting through the things of the two of them, Yu Fei was not prepared to take any extra things with him, because he had to take an unconscious person away. The water was not as good as the ground, and people had nowhere to rely on, so it was very difficult to move in the water.

The difficulty of carrying one person inside is comparable to carrying three or four people on the ground.

Yu Fei helped Ma Laodao put on the clothes he had worked hard to dry, and put his oxygen tank on Ma Laodao's body. He fixed a lamp on him and himself, and then tied the two people together.

This way you can free your hands.

Yu Fei brought these things with him and decided to give up on the rest. Every time it was less difficult, he would be able to go more smoothly.

Because only Ma Laodao had oxygen to breathe, Yu Fei was holding his breath, so he had to leave immediately.

After preparing everything, Yu Fei quickly walked out of the cave and jumped into the water without hesitation, carrying Ma Laodao on his back.

As soon as he jumped into the water, Yu Fei felt that he was sinking. He hurriedly pulled the water hard to prevent himself from sinking to the bottom. Who knows what was underneath. If it was mud and he was trapped in it, it would really be a disaster.

The sky and the earth should not be called, and the earth and the earth are not working.

Because he was carrying Ma Laodao on his back, Yu Fei's movements were somewhat limited. He could only move quickly along the current. Fortunately, he had lights and waterproof eyes, so he could move along the current while observing the surrounding environment.

But there was actually nothing to see in this underground river. He was about to enter the underground river soon. Yu Fei hurriedly jumped in, predicting in advance and heading straight for the entrance of the underground river.

Last time I didn't understand the situation and was hit hard near the entrance of the cave. If I don't prepare in advance this time, Ma Laodao will probably suffer.

Moreover, if the oxygen tank was leaked, Ma Laodao would definitely die. He didn't want to swim around with a body on his back. The scene would be irritating to imagine.

Because of Yu Fei's abnormal vision and the assistance of lights, this time she found the entrance to the underground river and swam directly in along the current.

However, the next journey is not easy. It is surrounded by either stone walls or water. If something unexpected happens, there is no way to escape or ask for help.

Boom!

Suddenly! Yu Fei felt his arm being touched by something.

He was swimming in the middle of the water, moving forward with the push of the water. There was no way it was the rocks protruding from the surrounding stone walls. Yu Fei's heart beat heavily, and he felt that he could hear his own voice, which was aggravated by fright.
Chapter completed!