Gather feedback on ideas and inventions that you plan to market yourself, or find partners for further development. Remember that anyone can read your post, so don't disclose any confidential information about your project.
Why would this be better than flying for long trips? On short hops across a bay it makes sense. If you're thinking about doing this to make cruise ships that don't pitch and roll then, you're talking about one enormous ship -- bigger than anything ever built. Can you give a few more details?