Even 3 days without a meal, people go apesh¡t, despite being able to live 30 days (more for some) without food, but it’s 3 days without water. I doubt they’re great at desalination in large amounts at once.
I’m willing to bet they’ve stockpiled mostly weapons over foodstuffs and water, especially considering dietary restrictions (no pork, halal, etc).
Then again, the pious ones do fast for long periods.
Not much of a fast. They think that not eating between sun-up and sunset is “a fast.” I call it a normal day of work.
I expect they (Hamas and their Iranian sponsors) are counting on international sanctions against Israel, and "humanitarian aid" from the United States. They don't need stockpiles of food and water in that case.
They are also counting on a worldwide propaganda campaign to prevent Israel from conducting effective retaliation. That should a pretty easy campaign since the only effective measures left are expulsion of the Palestinians or their extermination. And there are no Muslim countries willing to accept the Palestinians.
So, extermination is what is on the table. Somehow it is acceptable for Palestinians to exterminate the Jews, but it is unacceptable for Jews to exterminate the Palestinians.
Go on and pick a side. Whichever side you like. There are not going to be any "good guys" when this conflict gets settled. The only question is who will be left standing.