One of two things is going to happen when companies decide they own (all) the fresh water (and people become desperate)
Either the company hires enough goons and/or thugs to keep their “investment” safe through lethal force and scare the plebs away, possibly employing bribing “lobbying” governments to do it for them
OR
The people who are right there next to water sources they are being told to pay more than they can afford to drink from will arm themselves and overwhelm the defending forces with sheer numbers, resulting in an internationally covered bloodbath, kickstarting Water War 1 as other companies rush to beat back any perceived defiance, nations attempt to secure access to fresh water whether it’s on their land or not, and normal people prepare for the worst.
(the point you were making) Their head