The 240-foot Hanseatic Marine Rabdan (formerly Silver) offers luxury, comfort, and fuel efficiency. The yacht, the world’s longest private aluminum vessel, was launched in 2007. It is very light for its size and has an aerodynamic design (the beam measures only 32 feet). As a result, it consumes only 130 gallons of fuel per hour, quite an impressive number for a 200-plus-foot vessel that can reach 21 mph. A newer version called Silver Zwei was recently launched by the Hanseatic shipyard in Australia.