The way of an eagle in the air; the way of a serpent upon a rock; the way of a ship in the midst of the sea; and the way of a man with a maid.
– Proverbs 30:19
[T]his verse gives the three and four list. Commentators are widely varied on the significance of this list and each item. Taken on its own, its puzzling. Verse 18 describes the list as things that are mysteriously incomprehensible and verse 20 draws a comparative conclusion. So, the list itself is not communicating something to us in some sort of code. Each item is connected by the word for way, which means habit or manner of conduct. The list presents four things in the natural way, or even instinctive way. The point then becomes clear from the rest of the saying in verse 20.