There is no reason to believe this is not a "real" company, in the sense that the apparent owner(s) are product designers who work within the shipbuilding design industry.
Although I see your point about starting a shipbuilding company in a landlocked country - a red flag for a simple hoax - there is no requirement that a manufacturing company actually manufacture in the country where it is registered. In fact, quite the opposite, companies will be registered wherever is most beneficial (tax, workforce, convenience for owners) whereas this may not be the best location for manufacturing the end product.
Is the website/company a hoax? Does it really exist and actually produce these submersible vessels?
I find it unlikely this is a simple "hoax"
- too much time and effort has gone in to designing multiple websites, renderings of 3D (the quality of which needs professional skill and software)
- Too easy to find actual contact details for the company & its owners - hoaxes tend to go out their way to make contacting them impossible.
Have they really produced the product they say they can?
- I cannot find any physical pictures of their product(s)
- They wouldn't be the first company to tout their product before physically manufacturing one. These days 3D renderings are as good as prototypes.
- I'm betting that if you had the money, they would deliver you a submersible yacht!
The website www.migaloo-submarines.com is registered to Christian Gumpold. The registrants of that domain list an email address on the domain motioncodeblue.com - this is registered to Christopher Gloning.
Searching for these two names together take you to blogs such as this one showing some impressive 3D renderings of yachts. There is also this one which credits the pictures as
exterior design by motion code: blue | DI christopher gloning, DI christian gumpold.
It's pretty clear these are two people who have/are making a name for themselves as creative yacht designers. They are both involved in a company called "motion code: blue" who, in the past have advertised for staff under that company name.