Just using a LOT of water is a bad idea (unless you eat a good amount, with salt and other nutrients around that time). Because as we all know, this can lead to hyponatremia (at the risk of stating the obvious: you sweat out a lot of salt with the water you lose. Only replacing the water dilutes your blood (serum).
As altitude  increases, the air becomes less dense because of the smaller amount  of air above that altitude. There is a corresponding decrease in  pressure with an increase in altitude. Eventually you reach a point  without air, and the pressure decreases to zero. That is space. + 91 others found this useful.
This is because a higher-than-normal temperature (a warm, balmy day) tends to be accompanied by a higher-than-normal barometric pressure of the atmosphere. That is, high temperature tends to decrease air density, while high pressure tends to increase air density. The air density ratio column in Table 3.1-1, which is the ratio of standard air density at altitude to the standard air density at sea level, shows that the air density decreases rapidly as altitude increases.