Each year thousands of people, many of them children, attempt to cross the Mediterranean Sea to Europe, trying to escape poverty and war in their home countries.
The journey is very dangerous: criminal gangs organise the crossings illegally, which means there's no-one checking that conditions are safe.
People are packed very tightly into small boats, which leak and often sink.
The biggest number of migrants arrive in Italy and Greece, because these countries are directly across the sea from Libya in north Africa.
Even if people do make it, they may not be allowed to stay in Europe. There are rules over who can and can't stay, so many have to be sent back to their own countries.
Ayshah has been to Sicily, an island near Italy, where many migrants flee to.
She has been finding out what problems migrants face if they survive the journey...