You're downvoted, but it's a good question. When I was in nautical school, we were learning the concept of propeller slip: you can estimate distance travelled b

You're downvoted, but it's a good question. When I was in nautical school, we were learning the concept of propeller slip: you can estimate distance travelled by the number of propeller revolutions, since the ship moves a fixed distance for each revolution at a particular speed. This is affected somewhat by wind, current and propeller inefficiency (slip). Anyway, Chief Engineer of a ship had noticed that slip increased slightly but couldn't account for it. It was a tiny amount, so not worth investigating. Then the ship comes into port and after taking on a harbor pilot, the pilot asks "do you guys know there's a whale caught on your bow?" The ship was riding fairly high and a whale, now long dead, had been stuck crosswise in the curve just above the ship's bulbous bow: (https://en.wikipedia.org/wiki/Bulbous_bow https://en.wikipedia.org/wiki/Bulbous_bow) So, if it has a negligible impact on performance, ship owner is unlikely to care enough to spend money on it.