In a moving address at Christ Church in Latchingdon, Essex, Paul Betts spoke of his pride and love for his daughter and described how he taught her how to deal with the world.
Comparing himself to a ship's captain the former policeman said: "He thought that he had prepared the little ship for anything that the sea could throw at it ... he trusted it with all his heart and believed that wherever it went it would return safely.
"All of a sudden a gigantic wave lifted the little ship into the air and tossed it on to jagged rocks ... His little ship was lost and would never again sail the sea," he said.
Family, friends and dozens of teenagers were among the congregation. Many stood outside the church, listening to service taken by the Rev Don Gordon broadcast on speakers.
Leah was later buried alongside her mother, Dorothy, at St Mary Magdelen church in Great Burstead, Essex.