very cool idea but unfortunately vinyl will not hold up to water on a long term basis water will damage it it be really cool if you got a year out of it though.
I see no way how water will damage it as long as water does not get to the underside. It had a pretty durable seal on top and if you can walk on it for years, I am willing to bet it will last way more underwater. Next step is build one for the snapping turtle, that will be a test. Already have the glass and wood waiting just need more silicone and some more vinyl sheets. But I got pulled over today for a crack windshield so that projects on hold haha.