Yes, and we love it.
You may be concerned about the impact of the salt on your galvanized metal tub, given that salts are known to accelerate metal corrosion.
Don't be.
https://www.morozkoforge.com/post/salt-water-ice-bath
However, never add table salt, or kosher salt, or road salt, or any chlorine or bromine containing salt. You might damage your Forge, and you might be risking your health.