In particular the author (IIRC a shipping financeer) addresses: Sea freight is a strictly price-sensitive industry that has used _centuries_ to find grey areas in which to shave a penny. Newcomers are chewed up and spat out. The story's protagonist, in their attempt to become a "shipping man", declines from being a wealthy fund manager to a broke divorcee.
My day job is at a freight-related SaaS. There is a lot of opportunity in freight outside of running your own asset-heavy line. We help optimise allocation. It's lucrative for us and for our customers.
But if I were to start such a thing, I'd find some "logistic managers" on LinkedIn and interview them about their pain. I expect finding a ship to send cargo would not usually be at the top of their list ...
... but it actually might be, right now, in the short term. Sea freight prices have soared over COVID, and are now 7+ times higher than before[1]. For someone determined to follow the romance of shipping, today might be a better time than most.
[0] https://www.amazon.com/Shipping-Man-Matthew-McCleery/dp/0983...