1. We're not talking about what's reasonable, but what's expected.
2. This isn't like a monopoly on water supply, because the ships don't have to go this way. To make the analogy work you'd have to add something like "everybody already has a well, but supplying tap water is cheaper than using a well". In such a situation, a water company that's maximizing profits would charge just a little bit less than using a well, and while it would annoy people it wouldn't harm them.
3. The government stops water companies from gouging for the good of the citizens, which isn't a factor here.
We could argue about how fitting it is, but I'll just say this:
If we want to go with "everyone has suitable access to rainwater for important household use", then it changes the impact of the water company overcharging. It goes from despicable to mundane.
The subject was predicting the cost of the boat getting stuck by comparing to the known cost to Egypt. The moral aspects of the water situation don't transfer across the analogy unless you also think that Egypt are charging less than they could because they think they have a moral obligation to shipping companies.
The houses just 100 yards away from me have wells for water. There is a large upfront cost of making the well but after that you have "free" water other than the electricity for the pump.
2. This isn't like a monopoly on water supply, because the ships don't have to go this way. To make the analogy work you'd have to add something like "everybody already has a well, but supplying tap water is cheaper than using a well". In such a situation, a water company that's maximizing profits would charge just a little bit less than using a well, and while it would annoy people it wouldn't harm them.
3. The government stops water companies from gouging for the good of the citizens, which isn't a factor here.