@AvocadoInTheRain:
They didn't use the coup de burst to get past these rough waters:
I said mostly. I didn't say 100% of the time every time.
They got past that one panel rough patch sure, and then in other situations? Like immediately upon losing Jinbe they get assaulted by a giant Octopus, a giant school of fish, a tsunami wave, a twisting river, a waterfall they need to go up, and then a whirlpool… all things they couldn't control and were just stuck along for the ride on, and only managed thanks to Luffy grabbing fish, that ended with the ship thrown on land and the crew separated. All things that Jinbe potentially could have helped avoid or lessen the severity of, or even known in advance were coming due to his feel for the water currents.
Oda showed when they escaped a wave from Big Mom how useful a good helmsman was, and then almost immediately emphasized the point by showing what happens when they don't have one. Same way he emphasized them not having a cook when Sanji left.
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@YoungWhite:
When was the Merry broken by bad navigation? I recall the damage being caused by outside attacks that had nothing to do with the navigation of the ship (Bellamy broke it, Laboon broke it, Johnny/Yosaku damaged it, Shura damaged it, Wapol ate it, the marines damaged it) and by the strawhats themselves (Luffy & chopper most notably).
The main damage that broke the ship came from the Skypeia journey and the crazy water spout ride they had to do to get there.
A lookout is one of the most important roles on the ship, I don't understand why you don't think they could use one.
I have never said they couldn't use one.
However, Oda has never made it an official position in any other crew, and Carrot hasn't shown herself to be particularly good at it.
Carrot's first appearance was her being a lookout, I'd say she's at least been shown to be competent.
Like how she spotted the giant octopus, school of fish bigger than the ship, the giant waterfall or the whirlpool and called out to warn about them in advance?
She has been shown capable of looking through binoculars. She has NOT shown any particular unique ability or affinity for the role that makes her especially good at it, or better at it than anyone else that's been in the crow's nest, and hasn't yet managed to spot anything significant in advance enough to actively avoid the problem. Instead, Nami takes over and starts calling out orders and where things are.
Jinbe only recently just got that scene after how many years?
Emphasized spotlight chapter was recent, but he piloted the boat without comment or trouble while travelling through the gates of justice back during the war. (plus the many, many water related feats we've seen him do from the same period like carry the group on door, water spout control, summoning fish, etc.) And Helmsman was an established crew role when we first met the BB pirates.