Why do plastic bottles have grooves?

I was asked this exact question at my interview for the master's program in product design at Indian Institute of Science, they asked me to give as many reasons that come to my mind. read more

- The mineral water bottle is made of 'thinner' plastic than the one used for aerated beverages. The reason for this choice can be the fact that water is not sold in pressurized bottles hence thinner plastic is economical. This weakness is structurally made up for by designing the bottle with grooves. read more

Water bottles have small indents to improve the stability of the bottle. The bumps or the corrugations in the foot of the bottle increases the strength of the bottle. Take a sheet of paper and fold it. read more