Your faith is weak. If your opinions were subject to a Free Market, we could solve this problem.
Smart people with the public good and long view can, however, do better in public policy that sets limits on wreckless actions.
If you want to see what happens when people don't give a shit look at China where Beijing recently had to close schools for several days because of the pollution.
This doesn't necessarily follow. Private ownership can be structured as something other than for profit. Non-Profit Land Trusts are big thing in many areas of the US for example. But even industry motivated groups might be a choice. Think a home-owners association of beach property owners (including resort hotel conglomerates) or fishing rights cooperatives. If either had stronger property rights and standing to remedy damages they would be motivated by longer term aims to ensure water quality. You might be right that this could have adverse consequences but I wanted the raise the possibility of options other than BigWaterCo.
If there's anything we know about politicians up for re-election in two years or unable to run for another term it's that they take a long-term approach to problems. /s