Cushion matting overlay - does it exist


Hi all - newbie here I'm in the UK but inadvertently posted this message in the US forum: silly me!
I need a sort of matting that I can cut up to overlay certain areas of my pond where heavy objects (boulders, pond edgings) will be located.

It's really important that:
(1) it doesn't "wick"
(2) It's a cushiony-type material so it squashes down to absorb the heavy weight
(3) It's preferably waterproof
(4) Black in colour
(5) Can be cut to size
(6) UV protected

I was thinking of that black carpet underlay stuff but am worried it might poison the pondlife!

Very grateful for your thoughts, suggestions. Thanks!!

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