If it's a glass tank, you are probably going to have to silicone a pane of glass in. And be prepared for leaks, as silicone won't seal/adhere to cured silicone very well.
I think this is the reason people do false-bottoms for the land section, so that it doesn't get flooded due to leaks and what not.
I like putting a sort of ledge or shelf at about water level, but that doesn't leave much vertical room for plant growth and what not. (and it can make cleaning a bit more difficult)