That's right, a gigantic steam-punk submarine!
Something like this:
You board it for a ride (it may be a new transportation vessel to a new underwater based city(inside a cave or under some sort of magic force-shield bubble)) and enjoy.
I guess i don't need to mention that the interior of the submarine is classic off the hook luxury, in beauty second to none.
A huge casino is located on the submarine as well as some spots for deep sea fishing.