rugf sand why the pantanal so clear?

Not sure how I ended up staring at videos underwater of the pantanal but one thing always baffled me and thats why it is so clear compared to any other bodies of water ive seen. This video isnt in english and I cant understand hardly any but I think he is talking and showing the sand bottom and how the water is filtered by it. Id love to know more and know if anyone has tried to replicate it with a reverse undergravel filter and deep sand bed. My guess is you would need a high head rated pump but why not turn the whole tank bottom to a sand filter?

BRASILIEN PANTANAL - Expedition 2011: http://youtu.be/i9cwsEs4tuY

Tharsgaard said:

Its springs coming from underground thats bubbling through the sand.

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Right and that water pushing through sand filters it right? I mean that water is unlike anything ive seen but then again I havent seen any other parts of the amazon with a boiling sand bottom. Just wondering if anyone has been able to successfully recreate something similar. Im afraid with heating cables you dont get much flow. I used a heating pad on my old nano tank but I dont think it created much if any flow

Ill have to do more homework this is something im probably going to try. I run deep sand anyways and that vid made my jaw drop with the clarity. I just wasnt sure if you could realistically recreate something like that or if you would need such a deep sand bed it wouldnt be practical. I feel like a typical rugf would move a couple inches of sand right out of the way and end up with a bunch of dunes in the sand. Or maybe im wrong. Engage research mode

That was what I was wondering but if it is just the fresh water flowing in that causes clarity wouldnt all flowing rivers be clear? And where is it coming from?underground I know but it isnt like a cycle somehow? I really need someone to translate for me because that is impressively crisp water and the video seems to be about the sand bottom