Completed in 2006, the Emma Maersk is the largest container ship ever built, and since the Knock Nevis is permanently moored, it is currently the largest ship in use. Capable of carrying up to 13,500 containers, the ship is 1,302 feet long, and its anchor alone weighs a whopping 29 tons.

At 160,000 tons, the Freedom of the Seas is the largest cruise ship afloat. Among the many amenities on board are an ice skating rink, a wave-generating pool for surfing, and a rock climbing wall. Freedom of the Seas will be knocked out of its position as the largest passenger ship in 2009 when its sister ship, the Genesis of the Seas, takes its maiden voyage.

The Swedish Navy slips below the radar with its Visby Class Corvette. The large, flat, angled surfaces of the hull reflect radar, making the Visby hard to detect. Think of it as the Stealth Bomber of the oceans.

At about 1504 feet long and 226 feet wide, Knock Nevis is the largest ship in the world. Completed in 1981, the ship was damaged in 1989 during the Iran-Iraq War when Iraqi jets bombed it. The ship was quickly repaired, however, and today it is permanently docked at an oil field in Qatar where it is being used as a floating storage ship for oil.

Dockwise Yacht Transport has been ferrying boats across the Atlantic Ocean since the '80s, but it is stepping up its operation with a new ship: the Yacht Express. When it hits the seas in the spring of 2007, the Express will cut the Fort Lauderdale-to-the-Mediterranean trip in half, to just eight days. In addition to speed, the new ship boasts luxury accommodations for 25 people wishing to travel with their yachts across the ocean. Unique to the Dockwise ships is a float on/float off loading system: In port, the ship lowers itself below the water's surface so that the yachts can simply sail off.

Is this the ship of the future? Wallenius Wilhelmsen Logistics is hoping that its concept ship, the E/S Orcelle, will be roaming the seas by 2025. The company, which specializes in shipping automobiles, envisions a totally green vessel that uses the sun, wind, and waves to power energy generators that include fuel cells. The envisioned ship would need no oil and would be emissions-free. If completed, the E/S Orcelle would be able to transport up to 10,000 cars across the ocean efficiently.

The Eirik Raude is the largest self-propelled, semi-submersible, oil-drilling rig in the world. Designed to withstand the harshest weather conditions, it is often deployed in the cold waters off the coasts of Canada and Norway. What makes this rig so unique is its high-tech positioning technology. The Eirik Raude does not use any anchors, instead six thrusters (along with transponders, satellite feeds, and onboard computers) work constantly against the currents to keep the rig in position as it drills.

The Vasco da Gama can suck sand up off the bottom of the sea and deposit it to build islands or ports. The largest dredger in the world, the Vasco da Gama can reach ocean depths of 130m, deeper than any other.

Don't let her old-world exterior fool you; the American Queen is high on innovation. Completed in 1995, she is the largest steamboat ever built and employs authentic steam engines, a 45-ton paddlewheel, and state-of-the-art Z-Drive propellers that steer her down the Mississippi River. Another innovation: The mechanized smokestacks split and lie flat for passage beneath bridges. The American Queen has been out of service since 2005 to help with Hurricane Katrina relief efforts. It will return to its mostly seven-day cruise schedules on the Mississippi River in March, 2007.

Although Cunard's Queen Mary 2 lost its title as the world's largest passenger ship, measured by tonnage, when the Freedom of the Seas took to the seas earlier this year, the QM2 still holds the record as the tallest and longest passenger ship in the world. The ship can accommodate 2,620 passengers and 1,253 officers and crew.