To explore the bottom of a 25-m-deep lake, your friend tom proposes to get a long garden hose, put one end on land and the other in his mouth for breathing underwater, and descend into the depths. susan, who overhears the conversation, reacts with horror and warns tom that he will not be able to inhale when he is at the lake bottom.

One atmosphere is also the pressure caused by the weight of a column of fresh water of approximately 10.3 m. A diver 25 m underwater experiences a pressure of about 3.5 atmospheres (1 atm of air plus 2.5 atm of water). The added pressure on tom's chest from the water would make inhaling low pressure air from the surface extremely difficult.