Plowing the sea. It's a metaphor for futility. The sea would just return to itself without being affected. The same is true when the ship plows through the sea. It roils up a pretty good wake, disturbs a few flying fish, sends out a "V" of waves, only for the sea to settle back into itself, forgetting we ever passed. There's something very symbolic about the whole matter. When we pass through life, is it any different? We make a few waves and then the world goes on with its business. There's something quite mesmerizing about standing on the rear deck and watching the wake. Of course, the same word is used for a rather felicitous funeral, but nothing has died here, except the time we have killed.