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Rock cracks, faults, or natural grottoes and caves can form areas where water bodies are emptied.

If you're lucky, you might even be able to find a karst cave that leads to the outside world from those places, which is the hope of life.

In fact, there is hope in the water, the earth's crust is by no means sealed, and those water outlets that can be seen from the outside world must have cracks that lead directly to the waterlogged layer.

The only thing that is a little uncomfortable is that most of those cracks are too narrow to accommodate an adult's body to drill out, and it takes some luck to really have enough rock tunnels, cracks, and karst caves.

"You're a clever idea, but there's one thing you don't seem to have thought through, even if we find a space in the rock formations that aren't filled with water, there is no air for us to breathe unless there's a crack in that place to connect with the outside world. Ye Shenyu thought for a while, and then couldn't help but shake his head.

This guy thought of the most rational step in a desperate situation, but this kind of thinking seems to be congenitally deficient.

The rock space under the water, if it is isolated from the outside world, there should not be any nourishment to breathe.

If you're unlucky, you might even pop up in the grotto, which is filled with biogas and natural gas.

"Hehe, your worries are right, but I have a way for this, there is no oxygen, let's make oxygen breathing by ourselves, the key is to find the area where the water is emptied first, it doesn't need to be too big, a few cubic meters of space is enough." Yang Di smiled.

"Make oxygen?" Ye Shenyu was surprised, "What do you use to make it?"

"Water. Yang Di said.

"Do you want to use electrolysis?" Ye Shenyu felt incredible, this guy really had a whimsical idea, and in this dark and desperate situation, he could even think of a way to create a chance to breathe.

"That's right. Yang Di admitted.

"Do you know how to use a spell on a lightning strike?"

"Yes, it's not too strong, but it's more than enough to electrolyze water. ”

"Then it seems that we really have a chance to survive in a desperate situation. Ye Shenyu sighed, and couldn't help but admire this guy a little, and he could even think of that kind of method.

How to breathe, this is the most severe survival challenge that the two of them are facing at the moment, even if it is a strong person in the Yunsha Realm, when the true qi is abundant, they can hold their breath for three or five days at most.

This is almost the limit, if the limit is exceeded, the monk will be dizzy, and at that time, the Grim Reaper will come to the door.

Of course, you don't have to worry about being thirsty under the water, there is fresh water all around, and it's better to be hungry, even if you don't take pills, with the cultivation of the two of you, you can be hungry for a month.

Of course, if you are really hungry for a month, you will almost be skinny and weak...

......

This kind of drifting in the dark, dry and depressing, the senses are deep in the cold darkness for a long time, and even the heart will be cold.

Yang Di and Ye Shenyu, they should really be glad to have each other right now, the water flow is slow, the surroundings are dark and quiet, like being banished to the edge of the universe, if there is no partner, then really no one can stand it, because everything is unknown and dark, and I don't know where it will drift to.

Perhaps it is precisely because of each other's dependence, this kind of quiet drifting, although boring, but both of them are extremely patient.

In the aquifer where you can't see your fingers, there is also no concept of time, and you can only figure it out with your consciousness.

Yang Di and the others felt as if they had been drifting for more than two days, and gradually, the water flow around them became more and more sluggish, and the water pressure did not increase too significantly.

This means that they have entered the bottom of this underground water basin, and it is estimated that they are already very deep from the ground.

The hydrogeography of the vicinity is very complicated, and the spiritual sense can detect many criss-crossing caves, karst caves, and stalactites.

But those grottoes and karst caves are almost all filled with stagnant water, which cannot meet the conditions of the two.

"Let's go in that direction. Ye Shenyu sensed it for a long time, took Yang Di's hand, and swam in one direction in the dark.

Since the current was now very sluggish, there were not much fluctuations, and if they did not move their limbs, they would be almost still at the bottom of the water.

Of course, this is not possible, staying at the bottom of the dry water is equivalent to waiting for death, the water has stopped, and they have to swim themselves to find a place to breathe.

After more than half an hour, after swimming a few kilometers in this underground water basin, Ye Shenyu finally sensed that there was an empty area nearby, and his spiritual sense probed it, like a large bubble in the underwater world.

It's mostly a cave.

Both of them were pleasantly surprised, and then quickly swam away, and after a while, they touched the mouth of an underwater tunnel.

The inside of this tunnel has been filled, but Ye Shenyu's keen spiritual sense can feel that above the end of the tunnel at a depth of dozens of meters, there is a space, which should be filled with a lot of natural gas and biogas, so it has been emptied out of a large karst cave.

Plop! Plop!

Coming to the end of the tunnel, the two kicked up, and soon their heads emerged from the bottom of the water.

The end of the tunnel is not wide, and the two of them seem to have emerged from an ancient well.

"Jump up!"

Yang Di excitedly transmitted the sound, the wet rock wall was very smooth, but fortunately, both of them were monks, and as soon as they stepped on it, they jumped from the water to the entrance of the cave more than three meters high.

After drilling into the entrance of the cave, Yang Di and Ye Shenyu were surprised to find that the inside of the cave was very large, with enough space for an apartment, and there were many stalactites hanging around it, dripping with water.

But the two of them did not rush to open their mouths to breathe, as they had guessed before, this natural cave was dark and damp, with almost no oxygen, but was filled with very thick methane.

Methane is colorless, odorless, and non-toxic, but it can't breathe, so after entering the empty cave of this underground water basin, except for getting rid of being immersed in water, it hasn't changed anything, it's still the same cold and damp, and you can't breathe!

What's worse is that after the surprise, Yang Di suddenly had the urge to scold the street.

The cave is very large, and there is naturally plenty of space for them to move, so they don't have to be crowded into a small place.

But this problem also comes, because the space is too large, it is very difficult to produce oxygen, it is estimated that even if Yang Di uses the little Wuji Thunderbolt hand to release the electric light until he is exhausted, his arm spasms, and the oxygen electrolyzed cannot fill this big cave.

Moreover, once oxygen is produced, the invisible thick methane around it becomes a time bomb, and the slightest spark is a sea of fire.

This stumped Yang Di.

"Looks like we're in trouble. In the darkness, Yang Di lit a cluster of True Qi Dao Fire between his fingers, illuminating the surroundings, and shook his head helplessly at Ye Shenyu.

Now there is no oxygen around, and even if you force out a fire, it will not detonate methane.