とひろのみずそこはわかってもひとひろのひとのむねそこはわからぬ

The depths of the human heart run deeper than the ocean

You can know the [water bed>水底 that is 10十 meters尋 deep, but still not understand the depths底 of the heart心 which is one一 inch尋 deep (尋 not an exact measurement here, just used for comparsion)

韓国