Nation (novel)
The main character, a teenager named Mau, was on a canoe trip when the wave came, so he did not die.  He comes back home to the island to find everyone gone.  The other main character, an English girl called Daphne, was shipwrecked on the island by the wave.  Soon, other people from other islands show up.  Mau, Daphne, and the new people rebuild the Nation together.