Over the Waves — Marianne Mitchell

In the summer of 1914, Joel Peterson's father offers him a challenge. Go with his mother on a visit back to Sweden and make sure nothing goes wrong. To Joel, it seems like an easy way to prove that he is old enough to make big decisions. Joel enjoys meeting his grandparents in Sweden and making new friends, especially a pretty girl named Kari. But lazy summer days end abruptly when World War I breaks out and Europe is thrown into chaos. Suddenly, Joel is faced with the monumental task of finding passage on a ship back across the Atlantic where mines and German U-boats lurk in the waters.