Israel supplies only a small percentage of Gaza water.

Israel left in 2005, the "blockade" (which ignores the third border with Egypt) started in 2007 after Hamas seized control and Israel found itself with an enemy worse than Fatah despite it's largest since the Sinai withdrawal to exchange land for peace.

Natanyahu "supporting" Hamas was a policy of containment (coupled with recent pre-Oct-7 increase in work permits to Israel amogst other overtures) and which led to the October 7th. Israelis think a ceasefire would result in resumption of containment and eventually another October 7th so no go.