Someone I read on John's Gospel attributed to Chrysostom the saying, "The Gospel of John is like a river in which a child may wade and an elephant may swim." I have never found the quote in Chrysostom. Andy Naselli has tracked down the quote in his blog entry On Swimming Elephants. He provides the quote from Gregory the Great that all but seals the case. This agrees with Craig Koester's research in his Symbolism in the Fourth Gospel.