If you’re standing on the prow of a ship, you're on the front section, above the waterline. When Leonardo DiCaprio declared himself “King of the World” in the movie Titanic, he was standing on the prow of the doomed ship.
Prow came into English from the Greek word prōira, from a base meaning “in front.” Prow typically refers to the front part of a ship — the pointy bit that cuts through the water. You might see the prow of a ship approach the harbor through the fog. You can also use prow for things that look like the front of a ship, like the prow of a rock formation.