However, not all tsunamis begin with a receding ocean. Some arrive as a rapid rise in water level, without an obvious retreat.
This is why people should never wait to see what the ocean does after a major coastal earthquake.
If strong or prolonged shaking occurs near the coast, evacuation to higher ground should begin immediately when it is safe to move.
In Japan, tsunami warnings were issued after the 2011 earthquake.
Authorities initially estimated the potential wave heights, but the extraordinary magnitude of the earthquake and the complexity of the rupture made accurate early predictions difficult.
As the tsunami approached the coastline, the warnings were upgraded.
For some communities, the available evacuation time was extremely limited.
Entire Coastal Communities Were Swept Away
The most devastating effects occurred along the Pacific coastline of northeastern Japan.
Cities, towns, fishing villages, and agricultural communities were suddenly exposed to enormous waves.
The incoming water did not simply cover roads and beaches.
It carried tremendous amounts of material inland.
Wooden houses were torn apart.
Cars were lifted from streets and pushed into buildings.
Fishing boats were dragged away from their moorings.
Industrial facilities were flooded, and large sections of coastal infrastructure were destroyed.
In some locations, entire neighborhoods disappeared beneath the water.
The photographs showing boats surrounded by debris and houses submerged in muddy water resemble the destruction documented in several Japanese coastal communities after the 2011 tsunami.
One particularly affected area was the city of Rikuzentakata in Iwate Prefecture.
The tsunami overwhelmed the city's coastal defenses and devastated large parts of the settlement.
Buildings were destroyed, residents were displaced, and a famous coastal pine forest was almost entirely lost.
Another heavily affected location was Minamisanriku in Miyagi Prefecture.
The town experienced catastrophic flooding, and many buildings were destroyed or severely damaged.
The tsunami also devastated parts of Ishinomaki, Kesennuma, Onagawa, and numerous smaller coastal communities.
The destruction was not limited to a single city.
It extended across hundreds of kilometers of coastline.
Some communities were almost completely transformed.
Places where families had lived for generations became fields of mud, broken timber, twisted metal, and scattered personal belongings.
Fishing Boats Were Carried Into Streets and Residential Areas
One of the most striking details in tsunami photographs is the sight of large boats sitting far away from the water.
Fishing vessels that normally operate in harbors can be swept inland when tsunami currents become sufficiently powerful.
A boat may appear enormous and heavy, but it can become an uncontrollable object when surrounded by a massive volume of moving water.
During the 2011 disaster, vessels were carried through ports, pushed against buildings, and deposited in places where boats would normally never be found.
Some boats overturned.
Others became trapped among damaged houses and industrial structures.
Fishing communities suffered enormous economic losses because their livelihoods depended on functioning ports, boats, equipment, and processing facilities.
Even after the immediate flooding ended, returning to work was often impossible.
Harbors needed to be cleared.
Boats required inspection or replacement.
Fishing equipment had been destroyed.
Coastal infrastructure needed extensive reconstruction.
For many families, the loss of a fishing vessel represented the loss of decades of work and investment.
The consequences extended beyond individual fishermen.
Fish markets, seafood processing businesses, transportation companies, restaurants, and suppliers were also affected.
A tsunami can therefore destroy not only homes but entire local economic systems.
Rescue Workers Entered the Flooded Streets to Search for Survivors
After the water began to recede, another difficult phase of the disaster started.
Emergency responders had to enter devastated communities to locate survivors, evacuate injured residents, and recover people who had been trapped beneath debris.
The rescue environment was extremely dangerous.
Floodwater covered roads and streets.
Buildings had collapsed or become unstable.
Electrical infrastructure was damaged.
Fuel, chemicals, household materials, and sewage could contaminate the water.
Large pieces of timber and metal were scattered throughout residential areas.
In some places, rescuers had to navigate through deep mud while searching for survivors.
The work required coordination among firefighters, police officers, medical personnel, military units, and volunteers.
Japan's Self-Defense Forces played a major role in the emergency response.
Personnel were deployed to assist with search operations, transportation, evacuation, and humanitarian support.
International assistance also arrived.
Countries around the world offered emergency supplies, search-and-rescue personnel, medical support, and financial assistance.
The United States launched Operation Tomodachi, a large-scale humanitarian assistance and disaster relief operation involving American military forces in support of Japan.
Rescue workers faced exhausting conditions.
Some searched for survivors in freezing weather.
Others worked through the night under temporary lighting.
Many had to move carefully through unstable structures because additional collapses remained possible.
For families waiting in evacuation centers, every new rescue announcement brought a mixture of hope and fear.
Some people were reunited with loved ones.
Others received news that they had been searching desperately to avoid.
The Human Cost: Thousands of Families Lost Everything
The most painful consequence of the 2011 tsunami was the loss of human life.
The earthquake and tsunami caused widespread destruction across northeastern Japan.
According to Japanese official disaster statistics, approximately 15,900 people were confirmed dead, while more than 2,500 remained missing in the years following the disaster.
The combined number of dead and missing was approximately 18,500.
Many victims were caught by the rapidly advancing water.
Others were trapped inside buildings or unable to reach higher ground in time.
Older residents, people with disabilities, and individuals who needed assistance evacuating faced particularly serious challenges.
In some communities, families attempted to escape by car, only to become trapped in traffic as roads filled with water.
Others ran toward evacuation centers, schools, hillsides, or designated shelters.
Some survivors were separated from their children, parents, spouses, or neighbors.
The emotional consequences were enormous.
For many people, the disaster did not end when the tsunami disappeared.