We use economics to understand how resources can be exchanged for human benefit. If google had offered 100 billion dollars for this water, none of us would believe it immoral for them to make this transaction because the money could be used for good by the community.
Obviously however, 100 billion dollars is too high a price so the problem becomes not if it is immoral for google to take this water but what price is this water worth such that both google and the community come out ahead.
In the case where the money goes to "the community", then sure, maybe. But are the people selling it doing it for the interests of the community? How is the money used to benefit the community?
I am a Socialist myself, so perhaps that's why I am sceptical of the claim that 100 billion dollars would be enough to offset any kind of moral questions. Is it ethical to accept 100 billion dollars from an exploiter of labour?
Obviously however, 100 billion dollars is too high a price so the problem becomes not if it is immoral for google to take this water but what price is this water worth such that both google and the community come out ahead.