There is no catch. Its the way ALL charter companies get new boats in their programs.
You buy a new boat. For the first 1-5 years, you make the payments; they operate and maintain it for you. And they charter it out. You can use it for say 12 weeks a year, or a sister ship worldwide. The revenue from chartering USUALLY makes your mortgage payment while the boat is in the program. Usually.
At the end of the program, its your boat exclusively. And your mortgage of course. You can keep the boat, sell it, or put it in a tier-two charter company that takes older used boats.
Charter companies like this because they get to use OPM (Other People's Money) to finance their fleets.
For owner/buyers, there can be tax advantages. Most end up liking having the first (say) 5 years of their 15 year mortgage mostly paid on a brand new boat. You still need the cash for the down payment, and you always own the mortgage. The usage model has to work for the prospective owner. And the boat gets used by people you do not know. It's not for everyone.