However, Sanad’s investigation shows that this is simply the access hatch for a water reservoir that the hospital uses to fill therapeutic pools for amputees, water the grounds, and a reserve water source in case of emergency.

This was pointed out immediately after Israel made their claim.

It clearly wasn’t hidden and looked exactly like the service access to an underground storage tank. Something most hospitals in Gaza need because Israel controls their infrastructure and may shut off water, electric, internet or any other utility at any moment for any length of time.