Aquarium Frogs Ideas On How To Build Custom Landing For Frogs And Turtles In Aquarium...?

Ideas on how to build custom landing for frogs and turtles in aquarium...? - aquarium frogs

I want to build their own destination for large frogs and turtles in a large aquarium. I suspect that some sort of foam or something similar, to include the fake rocks and waterfalls, you can buy for reptiles, fish and amphibians. Of course, the materials must be safe for animals and OK in the water. I want the final product look like natural rock. All ideas for materials that could serve such a thing?