What causes the tube to blow bubbles when it is underwater?

Question

Arieonna · Answer

this is what I read "Bubbles are remarkably subtle things. They represent an equilibrium between air pressure pushing outwards and water pressure and surface tension pushing inward. Note that the water pressure at the bottom is greater than at the top of the bubble, and that the air pressure is almost identical; that means that the bubble tends not to be spherical. Moreover, bubbles (because they are lighter than the water they displace) tend to move upward through the water. This also flattens them"

Nightmoon · Answer

Okay, thank you-