You'd be better off having lidded containers with no water. Since it stops the air loss every time it's opened. But you don't lose the energy when you take them out.
Water is ~ 1000 times heaver than air so for a fridge, removing the water is the same as letting out air 1000 times.
Freezer is worse because there is also the phase change in the water. But having ice is useful.
It depends what you're optimizing for. If you're primarily interested in resilience to power outages, then maybe you are OK with the wasted energy used to freeze/re-freeze the extra water.
Water is not a good choice to optimize for this. Most energy from the ambient air gets consumed at the thawing point of the medium - 0 degrees for water. So water/ice will keep freezer at 0 degrees for longer, but that’s not an attractive goal for a freezer - you want some cooling medium that does the phase change at a colder temperature (adding copious amounts of salt to the water would go a long way)
Professional cooler packs can have that point down as far as -35 Celsius.
Yeah well, water is practically free, readily available, relatively benign if it leaks, and can be a hydrating life-saver in a pinch. So it's a pretty good option as something other than air.
Keep in mind that everything with some amount of sugar or salt has a thaw point below 0 degrees. Practically all of your food will have thawed by the point the ice melts - so you’re dumping a lot of energy into freezing water that will be mostly useless at the point disaster strikes.
Adding salt to your water will substantially lower the thawing point and it’s still cheap and widely available.
If you want to prep for cases when you need water you’d be better off keeping your freezer cold with a suitable medium and have a few 30liter buckets of water with some sort of additive that prevents spoilage (silver ions for example) or have some packs of bottled water around.
Water is ~ 1000 times heaver than air so for a fridge, removing the water is the same as letting out air 1000 times.
Freezer is worse because there is also the phase change in the water. But having ice is useful.