Complex sentence: Meanwhile, Chris's father, who has lost his boat, after landing on an island, soon sees Chris's boat, he paddles on the river, clumsily, until he lands up in the river with a long pole.
Split into simpler sentences: Meanwhile, Chris's father, who has lost his boat after landing on an island, soon sees Chris's boat. He paddles clumsily on the river until he lands up in the river with a long pole.