[ecomodded]

I had a look at the pdf file,without doing a 100% read of it more of a skim really i could not find what PCM substance they were using at sea. I suspect sea water ? as a sea water hose was on the parts list.

My concern with cooling the water storage is the energy needed to maintain its mass. Once its down to fridge temperature it is still going to warm with the fridge although slower it will need a longer cycle to completely cool and require a faster duty cycle to kick in, as the water saps the fresh extra colder degrees the fridge gained with the compressor run time.
So with my overly cautious concern over the energy expended cooling the extra water mass i am going to try sealed containers full of easily if not instantly cooled air.
For my freezer i think the frozen water is a stupendous idea that i do do and may well be best for the refrigerator half as well.
After my fridge gets its baseline run time numbers finished with its new exterior insulation i just did i am going to add air tight mass and see how that effects things. I am sure at that point i will want to add water and see how that goes.