While waves that travel within the depths of the ocean are longitudinal waves, the waves that travel along the surface of the oceans are referred to as surface waves. A surface wave is a wave in which particles of the medium undergo a circular motion. Surface waves are neither longitudinal nor transverse.

Longitudinal waves occur when the oscillations are parallel to the direction of propagation. While mechanical waves can be both transverse and longitudinal, all electromagnetic waves are transverse. Sound, for example, is a longitudinal wave.

Water waves are surface waves, a mixture of longitudinal and transverse waves. Surface waves in oceanography are deformations of the sea surface. The deformations propagate with the wave speed, while the water molecules remain at the same positions on average. Energy, however, moves towards the shore.

Transverse waves cause the medium to move perpendicular to the direction of the wave. Longitudinal waves cause the medium to move parallel to the direction of the wave.

Examples of transverse waves include:

• ripples on the surface of water.
• vibrations in a guitar string.
• a Mexican wave in a sports stadium.
• electromagnetic waves – eg light waves, microwaves, radio waves.
• seismic S-waves.

Water waves are an example of waves that involve a combination of both longitudinal and transverse motions. As a wave travels through the waver, the particles travel in clockwise circles. The radius of the circles decreases as the depth into the water increases.

But like all water waves, a tsunami has elements of transverse wave motion and longitudinal wave motion. In a transverse wave, the particles move perpendicular (at right angles) to wave direction.

A tsunami with a record run-up height of 1720 feet occurred in Lituya Bay, Alaska. On the night of July 9, 1958, an earthquake along the Fairweather Fault in the Alaska Panhandle loosened about 40 million cubic yards (30.6 million cubic meters) of rock high above the northeastern shore of Lituya Bay.

100 feet high

SAN FRANCISCO — Huge tsunamis with waves as high as a four-story building could inundate the island of Oahu, washing out Waikiki Beach and flooding the island’s main power plant, a new study finds.

84 feet high

A rogue wave could also cause a cruise ship to capsize. A rogue wave is an extremely rare occurrence but can prove extremely dangerous to cruise ships in the open ocean.

Cruise-ship sinkings are much rarer, but in recent years some cruise liners have been hit by rogue waves, including: The Caledonian Star, sailing in the South Atlantic in 2001, was hit by a rogue wave estimated at 100 feet; it cause extensive damage to the bridge and navigation controls as it swept over the ship.

Cruise ships can easily handle waves that are over 12 feet high. However, with waves of this height, you may begin to feel the ship rock and if you’re prone to seasickness you may start to look for relief.

Severe weather has sunk more than 200 supertankers and container ships exceeding 200 metres in length during the last two decades. Rogue waves are believed to be the major cause in many such cases. Mariners who survived similar encounters have had remarkable stories to tell.

Well, it doesn’t prevent people from worrying that at some unlucky moment, such a jumbo ship can flip over. What these people don’t know is that a cruise ship can roll to almost 60 degrees before it’s in danger of tipping over. Plus, cruise ships are built to withstand 50 foot (15 metres) waves.

So it is highly unlikely a properly handled US aircraft carrier could be sunk by a 200 foot wave. Damaged heavily to be sure but to take one to the bottom would require extraordinarily bad seamanship and bad luck to converge at the same time.

For context, some 40 or so cruise ships sail around the coast of South Africa every year, and none has ever sank due to a freak wave. So cruise ships are designed to weather 15-metre (50-foot) waves, which are in themselves rare, and extremely unlikely to be encountered by a cruise ship.