Does water protect against nuclear radiation?
We get asked this question a lot. I know that you have to factor in a few different factors. So keep that in mind. We will cover all the factors to determine if water can protect you against nuclear radiation.
A Few Feet UnderWater To Protect Against Radiation?
Water doesn’t protect you from radiation. In fact, it may do the opposite. When exposed to radiation, the water’s molecular structure changes and becomes radioactive.
So if you’re just a few feet underwater, like in a swimming pool, it won’t protect you from radiation. The only way it could be effective is if you were thousands of feet(or more) below the surface.

How Can Water Protect You From Radiation?
The main way that water can in fact protect you is through drinking it. If a nuclear bomb is dropped and your water becomes contaminated you will need a clean source. Otherwise, you risk getting radiation, poisoning.
So water, can save you if stored for drinking purposes. In defense against radiation, it is far less of a barrier than concrete walls.
Deep Under Water
As mentioned above I would suspect that going far underwater would be a barrier for harmful gamma rays and the like. If there was a nuclear war for instance being far below the surface of the ocean could do the trick.
I know the major problem would be how far you would need to go in order to be safe. If it’s not far enough, even by a little the radiation will get to you. There is no way of knowing how far you would need to be underwater. I say a few thousand feet if not more.
Further and Further You Go!
The further the better and the chances of sustaining that are unlikely long term. If a nuclear war occurred and you sought rescue by going thousands of miles in the ocean you may have a chance. The sad reality is that you would need to get more oxygen from above (eventually). In this case, the air around you would be contaminated and you will risk the after-effects of the nukes.
The only scenario this would work is if there was a deep underwater city, with an area to produce oxygen and food. Otherwise going deep below the surface will lead you back to the top.

The Further You Are Away From Radiation The Better
This applies to water and any structure designed to prevent harmful gamma rays from hitting you. So a deeper bunker or more concrete are all ways of doing this.
Would I Use Water To Protect Against Radiation
Not a chance, because in reality, it is not likely to protect you. In most cases, you will die if you rely on water to protect you from radiation. I would not put water, in the category of protection from radiation by any means!
Does Water Protect Against Nuclear Radiation
So, does water protect against nuclear radiation? No, it will not. In the vast majority of cases water, will not serve enough of a barrier to protect you.