She didn't expect to find herself living under the sea. She didn't expect much when she fled Ukraine on the first day of war. As the sound of explosions sent her heart racing, she knew she had to grab her son and run.

She didn't pack anything because she was struggling to think clearly. She bundled her child on a bus that took a precarious route through the backroads of Ukraine to avoid the traffic jams on the main road to Poland. She tried to keep her child calm by telling him that they were on a special trip.

She reassured him that we were going to see him.

Vladimir was nearing the end of a stint of building work when he was separated from Julia. He was going to return to his hometown of Vinnytsia a few days later. He raced to Poland to be with his son. He brought the family back to the Netherlands.

Ukrainian refugees are trying to find their way in Poland.

Julia, Vladimir, and Danilo lived in the hull of the M.L.V Castor, a restored Cold War-era Dutch gunboat docked in the center of Rotterdam's gleaming harbor. The Dutch state is trying to find beds for 50,000 Ukrainians in a country facing a housing crisis. municipalities across the country have come up with their own unique solutions.

The response shows the huge logistical challenges ahead as Europe faces its biggest refugee movement since the Second World War.

In the past few months, more than 5 million people have left Ukraine for countries in the European Union. More than 3 million people traveled to Poland, around 825,000 fled to Romania, and more than half a million are in Hungary. The E.U.'s Temporary Protection Directive gives Ukrainians the right to live, work, and attend school in any other E.U. country.

Europe's embrace of Ukrainian refugees shows a better asylum system is possible.

As new movements take place every day, it is clear that many people are moving on. 385,000 Ukrainians have been registered in Germany. 134,000 people are in Spain. Over 48,000 Ukrainians have registered in The Netherlands.

Julia arrived on the M.L.V Castor on March 16 and was assigned a berth by the Rotterdam municipality after staying in a cramped room for a few weeks. The couple worked together for the best interests of their child while they were separated. Julia thought as she crossed gangplank that it was really possible to live here.

The family's cabin is in the water. She says that the first night she couldn't sleep because the water was slamming on the walls. I'm under the water!

The owner of the ship says there was a similar reaction from many of the people who were assigned to his ship. He is confused. Living on the water is not a big deal in a country with over 300 miles of coastline, 3,700 miles of inland waterways, and one third of the land below sea level.

The Ukrainian people never realized that it is possible to live on a boat. They got sick.

The former naval engineer is fond of telling the history of the M.L.V Castor. It was built as the Dutch prepared for the Cold War and the possibility of Russians throwing atomic bombs.

The M.L.V Castor is a floating hotel, a party boat, and a museum ship. It was one of the few sailable vessels from its era that was used in a movie.

They knew they had to come up with innovative housing solutions when they started preparing for the arrival of Ukrainians. The Netherlands is facing a housing crisis, with nearly a million new homes needed by the year 2030. Many of the 35,000 refugees from other countries are living in appalling conditions in tents.

The first option was to book a lot of hotel rooms. They were brought from the hotels to the cruise ships.

The M.L.V Castor is one of four river cruise boats that the city is hiring to house Ukrainians. 1,400 Ukrainians are now living aboard a cruise liner after it persuaded it to sail one of its vessels into port.

Only three buildings survived the bombardment in the Second World War. It is a part of our history. We feel for the Ukrainian people.

Julia is grateful for the welcome she has received from people in Rotterdam, which is visible on the boat: the Mess is littered with donated toys; tub of toiletries brought by neighbors fill the shelves of the three bathrooms. Julia got three jobs when she started looking for work, and all of them were in the karaoke lounge.

Every day there is a communal breakfast and dinner served up by Van Parijs's wife Eelke as Ukrainian mothers dodge in and out of the galley to make meals for their children.

Julia is in the middle of it. She looks a decade younger than her 35 years because of her warm and effusive smile. She seems happy and at home on the boat, affectionately chiding the ship's dog Butz, a heavyset brown Labrador who navigates the steep stairwells with considerable more ease than the Ukrainian children do.

Julia is not at home and she is not happy. There are always thoughts of the war behind the smile.

When she goes out to her jobs in bars and cafes, she is amazed that people can be out having a good time, and wants to know how they can carry on.

Ira Koval, a Ukrainian woman who volunteers with the Ukrainians in the Netherlands Foundation, which existed before the war but has mobilized to help the new arrivals, says she sees the same trauma in many of her countrymen.

She says that life here is like a movie that is being played to you. It is an extremely difficult situation.

European nations that host Ukrainians will have to deal with trauma and education for millions of children who do not speak the language of the country in which they have fled.

Housing is the immediate need. Julia and her family must leave on June 16. They don't know where they will go. Thousands of people across Europe who have housed Ukrainians in their own homes are starting to feel the strain because Ukrainians cannot live on boats for more than a few months. They concede that they have not found the solutions they are working on.

The integration of the Ukrainian refugees may prove to be the most politically testing phase for the European Union, as it presents the possibility of tensions between the needs of the new arrivals and existing problems in their host nations. Many Dutch people and refugees from other countries have been waiting for years for stable housing and the balance of providing homes for Ukrainians is in the Netherlands. Germany is also facing housing challenges. When 12% of Spain's population is unemployed, the government must justify assisting Ukrainians find work. If they are to prevent a backlash and surge in nationalist sentiment, E.U. nations must find ways to navigate these delicate challenges.

Even if the war ends, there will be mines in the ground and Julia cannot imagine a safe return. I will be so worried about my child every day.

She can only return in her dreams, and the last time she thought about her homeland was a desolate place. When she woke, she was overwhelmed by an emotion she had never experienced before.

We can be reached at letters@time.com.