Personally I'd use marine grade epoxy make sure (SURE) it is mixed absolutely correctly and very carefully. It should cure in a warm place and it will need at least 10 days to fully cure after you will need to wash it down with hot water, very carefully and then a whip down with acetone, and then a second wash. Epoxy is 98% waterproof and that is about as good as you can get with a durable finish. You will not need to worry about water even in a semi aquatic set up (like for frogs or turtles). It builds very fast so one heavy coat is usually all you need I used to use a foam roller and or a putty knife to apply. If you want a real amazing finish you can apply a heavy coat and after it is cured (10 days) sand it with a fine sandpaper (800 wet) and then buff is shiny again (rottenstone) It is tons of work but is super smooth and shiny, very easy to clean. Just do not cut through the coat. (I use a sanding block not a power sander)

Yes it is a lot of work and cost is not cheap, it is exceptionally hard wearing and very tough permanent surface.