There are many reefers who use NSW in their systems. But, unless you have ready access to it, and collect it on your own, it can become very expensive. How big is your system?
I would not assume that water is from the Caribbean, but I do not know of any reason to not use it aside from the likely high cost relative to making your own. I've not seen any analysis of this brand.
IMO, it may lack some of the benefits of natural seawater that you collect yourself, which contains lots of natural bacteria. This one may not have such bacteria.