A prototype supermarine that allows adventurous fish to explore dry land:
The obvious problem with this model is something called the "free surface effect" in the nautical field. Any naval or merchant marine officer can tell you that the solution to that is a full compartment with no free surface at the top, that is, a sealed tank. That unfortunately leads to an obvious secondary problem, namely the need to ensure there's enough oxygen dissolved in the water, but I can think of ways that might be achievable.
To anticipate a question, yes, the fish can see out of the tank. In fact, I was once looking at a giant salt-water aquarium tank with a girlfriend when I realized that this one particular fish was pretty seriously ogling said girlfriend. I pointed this out to her and she expressed skepticism, so we did an experiment: She walked around to the other side of the tank (which was probably six feet high, with width and depth in proportion), and sure enough the fish followed her. The whole time we were there, the fish didn't take its eyes off of her. You know how in 1950s sci-fi movies the non-humans were always after our women? I'm telling you it's true. But I digress.