Once again, marketing clouds the waters, or stones. Ray Mears sells a set of stones with his name on it. They won't sharpen knives or impart some superior bushcraft ability on your knife any better than other tried systems.

Now, of greater import and not thought about: Never loan your best knife or let it leave your side. I have a Kauhavalainan puukko.It's my pet knife.
A few years back, I folishly set it down long enough for a idiot with some new wonder sharpening tool to grab it and demonstrate. He was convinced all knives were inherently dull, like somebody with a new religion. He ran his thumb disdainfully on the edge. The slice required; microsurgery, 5 stitches and antibiotics. HE STILL ran my poor knife through this pocket grinder and wrecked an edge time and use had lovingly set, before going to the emergency room.

One thing that is getting missed here I suspect is that Japanese water stones are just another form of stone.

Just because something is a Japanese water stone doesn't mean it is ultra-fine and leaves a mirror finish. That is less a matter of the type of stone, Japanese water stone versus diamond versus Arkansas, than the grade of the stone you buy.

Yes, there are 8000 grit and finer Japanese 'gold' stones that will put a fine mirror finish on steel but they also make 80 grit stones that will quickly take a nick out of an axe and leave more 'tooth' than anyone wants on anything but a bread knife.

The main consistent feature of Japanese water stones is not so much that they are exceedingly fine, as some are, but that they are traditionally quite soft with a relatively weak bond between grit particles. Being soft worn particles break off quickly, form a slurry that does a lot of the work, and constantly adds fresh, sharp particles to the mix. For any given grade Japanese water stones tend to cut faster than other stone types. which translates to less effort and time spent sharpening once you have the technique down. On the down side this means these stones tend to wear unevenly and will need to be touched up with a nagura stone and, in time, made flat again.

The original Japanese water stones were entirely natural products and ones that were consistent in grade throughout, free of larger grit particles trapped inside, being both quite rare and dear. These have been replaced by man-made stones since the early 20th century. While a very few of the natural stones are reputed to have exceptional, possibly even mystical, characteristics and they have over time become revered religious icons, with prices to match, even traditional sword makers have largely shifted to man-made stones because of their superior consistency.

Norton is the main US company that makes water stones. Typically these are a bit less tender than the Japanese versions but they still maintain most of the favorable characteristics of a freely wearing, soft, stone.

I like water stones but it is mostly a matter of aesthetics and liking the steps involved that make it something of a ceremony. Quick and dirty you can get a good edge any number of ways. Diamond stones have come a long way since they first came on the market. An interesting variation that travels well is to buy a heavy sheet of glass, at least 1/4" thick and 6" square, 5/8" thick and 12" by 12" is better still, and to use the commercially available diamond lapping compounds. These compounds come in syringes and are fairly inexpensive given that you don't need much.

Another possibility, one I have used in the field where water stones are too delicate to carry around, is a sheet of heavy steel and a folder with a few sheets of wet/dry silicon carbide or diamond polishing paper in various grits. As I remember it I got along pretty well with just 120, 220, and 320 grits but there are grits as fine as 1200 available.