An act of smoking cannabis.
To create the tube, one takes a two liter soda bottle, and cuts the bottom half off. On the cap of the soda bottle, one pushes a small socket for a socket wrench through. After one puts the newly made cap on, place the whole bottle into a bigger bucket filled with water.
The cannabis goes into the socket and is lit. Then one picks up the bottle so its hardly in the water, lights the cannabis. One then lets the tube fill up. When done lighting, you rip, or take the cap off, put ones mouth on the soda bottle, and push the tube down so the water pushes it up into one's lungs.
Person A: Oh my god i saw that kid Ripping a tube in an elevator!
Person B; Hot box that shit.