Marianas Trench [sic] Navy did it once in the 60s or so then I think some Hollywood directory just did a couple years ago
We went into the trench but never touch the bottom. We still can figure out how to protect equipment from pressurization after x amount of km under sea. There's something like 15,000 psi for every km you go down...its insane. It will be a long time before we reach the "bottom" and even then it's going to become a matter of having the tools to explore it properly.