Fastest Boat in the World

Boat design isn’t just about speed, there’s also stability and tenderness. On high speed boats, the appendage drag, aerodynamic drag, and appendage lift forces can be very large. The use of computer modeling programs lets engineers to create radical new boat designs that previous generations of engineers would have never thought possible.

The current  fastest boat is the "Spirit of Australia". The water speed record was recorded on October 08, 1978 at Blowering Dam in New South Wales, Australia. 
Ken Warby set the world record of 317.6 mph (511.1 km/h). Warby designed the hull of his record-breaking boat, Spirit of Australia, himself and built it in his backyard. The Spirit was covered with a canvas tarpaulin when it rained and was made of wood and fibreglass, powered by a 6000 horse power Westinghouse jet engine (from a Neptune Submarine Patrol plane).

World's Fastest Drag Boats

Offshore powerboat racing is a type of racing by ocean-going powerboats, typically point-to-point racing. It's like NASCAR on water. Modern races are short, track style events with much improved viewing for the spectators, and the different categories of boats have multiplied far beyond the 4 classes. 
Super Boat International produces powerboat racing events for the fastest offshore race boats in the World. Teams are broken down in multiple classes based on size, engines and horsepower. Depending on the class, Super Boats vary in sizes up to 50’ feet in length and can reach speeds of 200 mph on rectangular racecourses, which average six miles in length. The cigarette or go-fast is a small fast boat designed for high-speed racing on the open ocean. A typical go-fast boats is built of fiberglass, 30-50 feet (10 to 15 m) long, about 8 feet (2,5 m) wide, with a long narrow platform and equipped with two or more powerful engines. People who like to race powerboats live for the adrenaline of speed. In the nautical world, this fast boat is the performance, exotic style and luxury.

The fastest boats are top-fuel vessels that run on alcohol or jet fuel. “Problem child” is one of the fastest hydro drag-boats with speed of 261 mph. 
Like race cars, drag boats race in classes based on what type of fuel is powering the boat. The premier category of drag boat racing being the Top Fuel Hydroplane class which is the water based equivalent to Top Fuel Dragsters capable of covering the liquid quarter mile in less than four seconds with a top speed of around 260 mph (400 km/h). The basics of drag boat racing are very similar to those of land drag racing, when the light turns green, a boat can pass the start line. These incredible machines sport the very same 8,000 horsepower, supercharged, nitro-burning, 500 cubic inch Hemi engines as a Top Fuel Dragster. Owning a drag racing boat is expensive. Top-fuel drag boats often cost $200,000 or more. If you decide to buy one of them... do it immediately!

The Fastest Yacht

 The typical speed for a superyacht of her size is between 20-25 knots and some yachts are strictly for lounging and luxury. The fastest yacht in the world title goes to "World is Not Enough"/Millennium 140, this luxury 42 metre (140') superyacht has a top speed of 70 knots. Millennium 140 is powered by two Paxman 18-Cylinder main diesel engines offering a combined 10,870hp with an extra 9,200hp added by twin TF80 Lycombing turbines. The design brief describes the hull as a modified full planing shape with a deep-V entry. Each item throughout sacrifices pounds to enhance the velocity of this extraordinary superyacht.  Embracing the image of speed, the engineers chose a superstructure of Alustar aluminum, for the upmost in lightweight alloy strength.


Fastest Military Craft

The Skjold class patrol boats remain the fastest armed craft in the world. "Shield" corvettes (Skjold) are a class of six large, superfast, stealth missile craft in service with the Royal Norwegian Navy. The prototype use 4 combined diesel and gas turbines combined by RENK COGAG propulsion system. The smaller gas turbines rated 2,000 kW turbines are used for cruising speed, for sprint speed a second, larger gas turbine is combined providing a total of 6,000 kW (8,160hp) to the waterjet on each shaft line. These provide a maximum speed of more than 60 knots (110 km/h). The Skjold class has been in service since 2010.

I can't imagine why this boat record hasn't been broken yet?
Where there is water, there is opportunity for racing.