Seeking advice. Converting swimming hole to natural swimming pond.

As the title suggests, I am going to turn this swimming hole my grandfather built into a natural swimming pond. In the past the "pond" has usually spent its life filled with green water that was swam in and usually kept cleanish with skimming and filtering typically used on a chlorine pool. At one short point in its life it was used as a chlorine pool and was crystal clear. To maintain that was difficult as it is expensive and the wind likes to send lots of debris and sand that clog traditional filters very fast. No chlorine has been used in a long time and we like to not use chemicals so it has been green with algae for many years now, and mostly unswam in because most of the children in this family have grown up and moved away. I am one of these "children" and would like to butify the pond and give it a more sustainable life so my family members that spend time looking at it will see something more beautiful and when family is in town it can be swam in again.

What I'm looking for is any advice on what I may need and also any books or information recommendations. I have attached photos of the pond. I'm no artist so I try to convey my message with emojis.

All help is greatly appreciated!

The pond is 9' deep at the deepest point and 1.5' at the shallow end. I think I would put my regeneration zone in this shallow end and build a small retaining wall to hold in a substrate for roots to grow. Anyone know what kind of medium one should use for regeneration zones?

The pump that is currently installed on the pond pulls water from the shallow end and sends the flow to the swimming area on the Opposite side. I imaging the current system would work to pull water past plant roots and circulate it back into the pool after being filtered by aquatic plants. If I am wrong I would love to know!

The pond has some guppies in it at the moment but I am going to relocate them back to a golf course pond which is where we believe they came from. My younger cousins were known to have done this in the past. We would prefer to have a fishless swimming pond unless of course they were needed for mosquito control.

We were also concerned about that brain eating amoeba but the pond is fairly cold all year and also the family has been swimming in it for over 30 years and we're all still amoeba free so we've mostly ditched that concern. If you know otherwise please let us know.

The concrete on the pond has experienced some cracking and has been patched in the past with various substances supposedly meant for the purpose of patching cement but the roots from the tamarisk trees still find their way into the pond. If anyone knows a little more about how I should patch these cracks please chime in. My concern is that the tamarisk roots may be bad for the water somehow but at the same time I feel as though they might not pose a problem at all. The pond still holds water very well and it seems my grandfather did a good job building the thing.

The "pond" https://imgur.com/a/ktQg5

Huge pond, well worth the effort. Gravel for the regeneration zone, plant helophytes in them, the tubers have the capability of oxiginating the rootzone, and  Irisses surpress duckweed. Get waterlilly's in baskets, held in place in one part of the swimmingzone. The shade will cool the water. Will help limit the evaporation.

Hugo thanks for your input. Will any type of gravel do? I have read that it needs to be a certain kind that attracts beneficial microbes. We have lots of rock suppliers out here but no one seems to know exactly the kind I need for this application.

At the water inlet side of the regeneration zone start with a coarse gravel then a layer medium, then fine , then back to medium, then your stones that block it. On the gravel a biofilm will establish. It's a slimy layer full of microscopic life, it works as a filter, absorbing nutrients from the poolwater, breaking down plant matter. If  all goes well, the remaining nutrients get sucked up by the plants.
By chopping down the plants and removing the foliage, by the end of the season for instance, you deprive your system of nutrients. Which reduces algae groth.
Do you mean scoria, a vulcanic porous rock, i understood it's hung in ponds in bags to suck up nutrients, but it has to be taken out and washed out every so often. Of what i've gathered it's not used in big systems, and i've not heard of biofilm prefering a specific kind of gravel.