Why do many potential friends think it is a "joke" to maliciously close someone else's diving tube at the depth of 15 meters underwater?

You can't joke about such things. This kind of behavior has involved personal safety and should not be joked. If it is a joke, it is too much. Because it's a joke with life.

Because Mr. Yu in Guangzhou is a diving enthusiast. He went diving in Southeast Asia, which should have been an easy trip. However, what he never expected was that the valve of the compressed air bottle on his back was quietly closed at the depth of PG Island 15 meters in the Philippine diving resort. Then he lived and died for dozens of seconds. With the help of the submersible, he reopened the valve of the gas cylinder and inhaled oxygen again. At that moment, he had choked a few mouthfuls of seawater and his eyes were red.

According to eyewitnesses, it was another diver nicknamed "T Tsai" who closed Mr. Yu's gas cylinder underwater. Within two days, he closed the cylinders of two diving companions at different depths underwater, on the pretext of "joking". Another victim and "T-boy" were strangers, but fortunately, they handled it properly and borrowed someone else's breathing head without causing more serious consequences.

Although "T-boy" apologized on several platforms afterwards, this behavior still exploded among diving enthusiasts. Many professional divers say that it is very dangerous to close other people's cylinders underwater. Floating in panic can cause decompression sickness, which may be life-threatening in severe cases. This behavior is tantamount to intentional homicide.

However, some professional divers speculate that Liu may think that he has a diving technical certificate and wants to "make things difficult" in front of novices without realizing the possible consequences.

No matter what Liu's purpose is, I think this method is wrong. Now we are really glad that there are no serious consequences.