Constructing a Butler style Natural Swimming Pool

I've been studying up on Mr. David Pagan Butler's Natural Swimming Pools and I think I might like to have one in my back yard.  My back yard, the soil of which is composed of a bluish gray clay, is very nearly always saturated with water after a hard rain.  This spring especially, I have not been able to mow due to the fact that much of the yard is in puddles inches deep.  This got me to thinking, after some prodding by my lovely wife, that if I cannot get a useful claim on the land, then I might at least get a useful claim on the water.  From my limited understanding of pond construction, a high water table, such as in my situation, precludes the use of a pond liner.  I'll be marking the spring high water level today, and digging a test hole this summer to discover how far the water level recedes over the summer drought.  Hopefully, it won't move too much.  If anyone else has built a Natural Swimming Pool under these conditions, I would be very interested to know what challenges you faced and how you went about overcoming them.

If it isn't a high water table and simply clay not allowing the saturation of water through it you'll likely dig through that clay line and then need to seal it with something. I speak from experience on that, unfortunately.

I 've helped build one with a liner. It catches rain water. It's magnificent. Rain water is less rich in nutrients than groundwater. especially if you get run off from a neighboring farmer who uses artificial plant nutrients. You can expect algae to flourish. Algae will rob your underwater plants of sunlight and warm up the water. Then you'll need more helophytes to push oxygen into the soil/substrate/clay, otherwise layers of dead algae will create anaerobic conditions. Anaerobic conditions will make things sick and smelly. Bubbling will help your system keep an aerobic system stablel. The drainage pipes connected to bubblers which creates a water flow in the drainage pipes, that nifty system mr Butler came up with, those drainage pipes are laying in vulcanic rock or gravelbeds. These attract a biofilm to grow on all this surface. It has an enormous cleaning capacity. I wonder how you envision to implement that vulcanic rock/substrate to lay still in clay without sinking into it and losing all that surface area. Clay is of such a fine constituency, i'm afraid the gravel/vulcanic rock will sink into it even with netting, it will come up through the netting, and will block the drainage system sooner or later.
I'm not saying a clay swimming pool can't be done. Sepp Holzer has ponds without liners that look clear to me , chrystal clear and he grows fish for the markets. But he is Sepp Holzer.
Have you checked out the olive and the washing machine tumbler water skimmer systems of mr Butler?  

Reports from my neighbors who have dug ponds on their properties suggest very deep clay and very high water table.  I could basically just dig a hole in the ground and it will fill with water.  That gives me confidence that I won't have issues as Elle may have experienced, but as Hugo has mentioned, the clay is a very poor substrate and will likely seek to infiltrate my gravel beds and make my water turbid and cloudy with silt.  I believe my best bet is to use a liner as a barrier against the clay infiltrating into the pool water and possibly using flagstones on a bed of pea gravel on the bottom of the pool to keep the membrane from detaching from the bottom, as this is a problem I've seen with a couple of the public pools in our area.   The pressure from the ground water pushes on the liner from beneath and causes them to balloon up from the bottom of the pool.  In this case, I won't be concerned about the liner leaking, no matter how old it gets, as long as it keeps the clay on one side and the water on the other it should do all I need it to.

I have not seen Mr. Butler's washing machine tumbler water skimmer.  Sounds very interesting.  I'll have to look that one up.

I think i have a different understanding of a natural swimming pool then you. If i would have your circumstances, i would dig a pond with a big shallow end and step levels down and observe the system while adding as much different species of plants i can get my hands on. Let them be in there. See what happens while your plants grow and establishes.Frogs, newts and all sort of wildlife will come. You’ll have a pond and maybe water clears, maybe not. There definitely are ponds that are natural and swimmable BUT, it’s not Butler’s system, his has a bubble system which pulls water through vulcanic rock.
If it doesn’t work out you will have a great pond which is incredibly beneficial for wildlife and frogs will roam your land and eat snales and such.You can then develop a new plan to do a Butler style ool with a liner. You’ll have tons of plants handy for cheap.

If it does work you’ve saved yourself an expensive liner and can start selling your plants.
Take your time and let nature work for you.

The only reason why I was trying to avoid using a liner is because they are known to start leaking after 20 to 25 years.  Which would require a complete rebuild in most cases.  I had hoped I could get away from using one due to the fact that most people HAVE to use one because they don't have suitable soil for holding the water in.  My main concern is in not allowing the soft clay sides of the pond to infiltrate into the gravel beds and make the water cloudy with silt.  By using a liner, I can keep the clay in it's place, keep the gravel beds from filling up with sediment, and keep the water clean.  In every other aspect, my design is much as David has done.  With bubblers ,and/or pumps to move the water through the filtration beds.    What I don't want is to walk out into my pool ankle deep in muck.  Lol.  The typical rectangular or circular swimming area should stay nice and clean.

Ok,  we made a walkbridge over the gravelbed onto the edge of the rectangular bit using acacia pseudorobinia with a ladder to descend calmly.  The Germans do a build called wall on liner, they build the wall on the liner (!) we weren't brave enough to do that. Do you think your liner will start to "float" if you make it all waterproof concrete and then glue the liner on top. I've read about that. We build the second wall on top of the liner( the small one that stops the gravel entering the swimming area), with lots of gravel in the regeneration are that will stop this one from floating. Have you build a lot of things?
The book how to build a natural swimming pool by Wolfram Kircher and Andreas Thon gave me a lot of ideas and insights as well.
Butler sells a video on how to build one, did you see that? He shows a lot of mistakes as well. Very funny and informative.

I have never built anything quite so large, but I am a quite a tinkerer and enjoy learning about and applying principles of science and physics to my builds.  I'll be doing a lot of research before even attempting this one.   As far as building the wall on the liner.  I suspect that would be ok in my situation, as I'm not dependent on the liner being completely intact.  I would think a bit of leakage this way or that to and from the pool wouldn't be catastrophic, as long as the bio-filter beds are up to the task.  I would like a circular pool.  So imagine digging a sloping circular hole, with a flat center, lining it all, building the block wall on the inside perimeter, then filling with water and back filling the outer perimeter of the wall with the gravel beds and bubbler pipes.  The weight of the gravel on the wall would apply compressive force to the block wall and equalize the stress on it.  For the floor of the pool, I would lay a bed of sand, or pea gravel, and maybe even set flagstone or sandstone slabs to cover the bottom.  The idea here is to give a close approximation of a solid bottom, and provide enough heft to prevent the rising swell of groundwater in the spring from ballooning the liner.  The one aspect I have to work out is how to have a sandy beach that walks directly down into the pool.  Having trouble picturing the transition area from beach to opening to pool wall.  So far I've only seen Butlers youtube video's and work's others have done.