Proposed in 2006, the proposed underwater hotel for Fiji known as Poseidon Resort Mystery Island has released new designs. Although it is still seeking funding to support the development you can now start saving your pennies for this vacation paradise. They estimate it will cost $30,000/couple for a week.
Cocoa Island's 23-room hotel that features suites resembling local dhoni fishing boats that are anchored to the ocean floor with pine poles. Best feature? Steps in the back of each suite/boat lead right into the water. Located in the Maldives.