Marcin Kolczyński had been relaxing on the beach in the Dutch seaside resort of Julianadorp when he spotted the children struggling and dashed into save them. His body was later discovered washed up in the shore.
The report also praised Bydgoszcz for being the safest and Łódź for offering the best value for money.
In the survey from Eurostat looking at families with three or more children, France topped the list, followed by the United Kingdom and then Germany. Poland came ahead of Italy, Spain and the Netherlands on the list of large families.
Prime Minister Mateusz Morawiecki on Friday morning visited the parents of Polish sextuplets at the University Hospital in Krakow, south Poland, and gave them the keys to a new nine-seater Volkswagen Transporter car.
The births took both doctors and parents by surprise as everyone was expecting five babies. Doctors say they are keeping the six new-borns under close observation and stress that they are so far doing well.
Poland is one of the best countries in Europe to raise a family, new research shows.