I used 3/4" White Thermally Fused Laminate Panel also known as Melamine lol. All joints were made using a dado or rabbit, joined with water proof adhesives, and sealed with white(non moldicide) silicone.
I have had standing water in them with no issues. Big snakes knock over water tubs on a regular basis. However I would not let it sit in there like that for long just to be safe.
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