Any mere millionaire can own a supercar these days. But how many can own a supercar yacht? In what could set a record for both speed and excess, a few supercar owners and companies have started building boats modeled after supercars like Ferraris and Lamborghinis. These aren't just wild concept drawings. These are actual boats that can cost four or five times as much as the supercars that inspired them.

Detail of the inside of Marine Technology’s Aventador boat, which is modeled after a Lamborghini, down to the iconic “start” button hidden under a small red lid. Source: MTI

"These are guys who just love their cars and want a boat to match," said Tim Gallagher, sales and marketing chief at Marine Technology, which has built multiple supercar-yachts. "It's different." Marine Technology's latest creation is the floating Aventador. Gallagher said that a few years ago, he had a boat built to look like his Mercedes. He liked it so much that when he got a bright yellow Lamborghini Aventador—which retails for more than $400,000—he asked Marine Technology to make him a matching boat.

Marine Technology displays its floating Aventador, and the yellow Lamborghini that inspired it, at the Miami Boat Show. Source: Marine Technology

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The result is a bright yellow beast in the water that has the same fighter-jet wedge shape and nearly the same speed as the Aventador. The company modeled every detail of the boat—from the taillights and headlights to the steering wheel and air vents—on the Aventador, Gallagher said. Even the dashboard is the same, with the iconic "start" button hidden under a small red lid.

Mercedes-Benz Cigarette Racing 50’ Vision GT Concept. Source: Mercedes-Benz

Under the hood, however, the floating Aventador boat makes the driving Aventador look puny. Instead of a 700-horsepower engine, the Aventador boat has two 1350 Mercury, twin turbo engines, creating up to 2,700 horsepower. The boat is "capable" of going 190 mph, Gallagher said. Of course, you probably wouldn't be in the water anymore at that speed. (Read more: Sale of $40 million Ferrari sets record) The total cost of the floating Aventador is about $1.3 million. "The engines alone cost more than the car does," he said. Mercedes-Benz has also gotten into the supercar-boat game. While the company was creating a concept car inspired by the Gran Turismo driving simulator, it also teamed up with Cigarette Racing to make a matching boat.