The cave was narrow, but it could be entered with an air tank on its back.

It's just that it's impossible to turn around in such a narrow hole after entering, so if you want to exit, you have to be dragged hard by someone outside, and if you carry an air tank, you can easily get stuck in the middle of the road.

But Poplar only cares about the safety of the iron bull, and does not consider anything else for the time being.

And this time he wasn't going to tie a rope to his feet, after all, he couldn't even drag it with that huge force just now, let alone the others who stayed outside the cave.

However, what Ding Sicheng said was reasonable, Tie Niu had been holding his breath for nearly ten minutes, and when he went in to find Tie Niu, if he couldn't let Tie Niu breathe immediately, Tie Niu would definitely not survive.

So Poplar quickly put the air canister back on his back, held a long javelin in one hand, nodded to Ding Sicheng, meaning to reassure Ding Sicheng, and then drilled into the hole.

The cave was so narrow that Poplar had no difficulty even turning around with an air tank on his back, so he could only rub his elbows and knees against the walls of the cave and sneak into the hole.

Luckily, it was easier to burrow in the water than on land, and Poplar dived in while keeping an eye out for the surrounding walls with the waterproof lights overhead.

He found that the walls of the cave were made entirely of black stones—in fact, the entire outer wall of the mound was made of natural stones, not of blue bricks. Presumably because natural stones can withstand seawater erosion better than green bricks.

It is not easy to make holes in the outer walls made of natural stones.

In the case of the poplar, the wall of the cave is uneven, but the protruding place is round and blunt but not sharp, not like a human being, of course, it is impossible to build the tomb deliberately set aside, but should be a kind of large marine animal that can drill holes to drill out for hiding.

And this creature should not be a moray eel.

First of all, it is not certain whether the moray eel can burrow in such a hard stone wall, and secondly, even the giant moray eel that suddenly popped out before is far less thick than this cave.

In other words, even if a moray eel were to burrow, there was no need to burrow such a large burrow.

As for what sea creatures got out of this big hole, Poplar can't guess.

After all, this submarine tomb has been around for nearly a thousand years, and there may be some strange sea creatures that have made a burrow here, and after a long time, this sea creature has left the cave and is picked up by a giant moray eel.

Poplar thought so, and continued to drill into the hole to a depth of about five meters, and the hole suddenly changed direction, from the previous vertical downward to diagonally downward direction.

Poplar continued on, but not far, when suddenly, he felt like he was swimming into a large space.

The large space seemed to surround the core of the mound, forming a powerful circulation. Poplar couldn't even get a closer look at what was going on around him, and he was swept along a circular groove by the circulation, and spun violently.

This turn went on for several minutes, and when Poplar turned dizzy and almost unconscious, he suddenly felt himself fall rapidly, and with a "bang", as if he had fallen into a deep pool.

Naturally, he sank sharply to the bottom of the water—

Of course, this is just his feeling, because he is at the bottom of the sea, how could he fall from a high place, fall into a deep pool first, and then sink to the bottom?

It wasn't until his body surged upwards again, and he felt his stomach churning and he was delirious, that he heard a cry ringing in his ears.

"Lao Bai, Lao Bai, you are sober! It's okay, we really entered this undersea tomb?"

Poplar suddenly woke up and kept his eyes open as wide as he could.

Vaguely, he first saw a figure, and when his vision finally became clearer, he realized that it was the dark but handsome face of his good brother Tie Niu who was in front of his eyes.

"Lao Bai knew that as soon as the rope was broken, you would definitely come in and look for me immediately, so I waited in place and didn't dare to move, and sure enough, you followed soon!" said Tie Niu, both relieved and happy.

Poplar looked blankly at the Iron Bull, then turned his head to look around.

"Lao Bai, we have entered the tomb, the air quality in this tomb is not bad, you can spit out the breathing tube and talk to me!"

Poplar spat out his breathing tube and tried to take a breath, and sure enough, the air was damp, but it didn't smell bad.

"Is this tomb so magical, what is it that sucks us here, and there is plenty of air in it?" asked Poplar.

"I don't know about this, I still need you to tell me!" Iron Bull said, smiling.

Poplar breathed a sigh of relief, and finally completely relaxed.

Looking around closely, he found that they were indeed floating in a pool of water.

There are several square walls around the pond, and between each wall and the pond, there is a long pond bank that is two or three inches higher than the pond water.

Looking up, the top of the head is also a boxy black top plate, and the height of the top plate is more than three meters.

And in the center of the top plate, there was suddenly a round hole, and he and Tie Niu should have fallen from this hole.

But strangely, he obviously felt that he was being washed down by the current, but now there was not a drop of water dripping from the hole.

After all, Tie Niu came down for more than ten minutes first, so he pointed to the hole and said, "It's strange, I just saw you fall from this hole, but there is no water to follow you down! And if you look closely, there should be water in this hole, but I don't know why, people will fall from above, but water will not!"

When Poplar heard him say this, he simply cast the light from the overhead lamp directly into the hole.

Sure enough, what Tie Niu said was right, he found that the light was reflected, and the water was shining, and indeed in this hole, it was full of clear water.

It feels like there's a layer of clear glass at the bottom of this hole. So much so that when people look up, they can see the light of the water, but the water will not fall.

But if the water can't fall, why do people fall?

Poplar Iron Bull has seen enough strange things, and it still feels incredible now.

"Are you sure you saw me fall from above?" asked Poplar.

"Of course I'm sure!" said Iron Bull, glancing at his hand, "You were still clutching this javelin when you fell, and if I hadn't dodged quickly, I would have almost been struck by the javelin!"

Poplar couldn't help but laugh, indeed, he still had the javelin firmly in his hand.

Thankfully, the javelin didn't hurt him when he was spun rapidly by the powerful current. And when falling from the hole in the top of the head, the javelin did not hit the hole horizontally.

"Where's your javelin? I remember you came in with a javelin!" asked Poplar.

"I don't know, maybe I threw the javelin away when it was so fast that it was being swept away by the water!" replied Iron Bull.

"Have you gone to the bottom of this pool?" asked Poplar again.

"Not yet!" Iron Bull smiled, "I thought you'd come to me right away, so I didn't do anything here......!" You're not here, I'm a little scared!"

Poplar knows that in the depths of this sea, and in an undersea tomb that he has never seen before, everyone will be afraid.

And with Tie Niu's temper, he would only admit to being scared in front of him, so Poplar naturally wouldn't make fun of him.

He simply took off the air tank on his back, swam to Tan Shui's edge first, and put the air tank and the javelin on the bank of the pond that was only a few tens of centimeters wide, and then said to Tie Niu: "Let's see if there is anything strange at the bottom of this pool, and then see if there are any mechanisms on these surrounding walls that can be passed." ”

Iron Bull agreed, and the two brothers took a breath and dived down into the pool at the same time.

It was soon found that the pool of water was only more than three meters deep, and the bottom of the pool was also flattened with black stones.

There is a javelin lying at the bottom of the pool, which is particularly conspicuous.

Tie Niu picked up the javelin, and Poplar carefully examined the bottom of the pool, which was not wide, to make sure that there was nothing strange at the bottom of the pool, and the two of them surfaced.

"I didn't expect my javelin to fall from the hole in the top of my head, but why, the water from above can't come down?" Iron Bull asked the same question again.

Bai Yang couldn't answer, so he could only say: "Since there are no strange things under this water, then we can only see if there is a way out on the walls around here!"

Iron Bull nodded, and the brothers swam out of the pool to the shore where the air canister had just been placed.

The shore of the pool was also paved with black stone, but it was too narrow for one to stand on with caution.

Tie Niu had also read Ouyang Qi's "Secret Technique", but Bai Yang knew that he was impatient, so he only read it cursoly, and he didn't study it thoroughly at all, so he didn't dare to let Tie Niu investigate the other walls alone, but let him follow him to investigate together.

(See Chapter 321 "Circular Passage")