[devit]

> on boat journeys even though 10% of the passengers would typically die on the way

Source? Seems highly implausible (in general).

[dredmorbius]

The "middle passage" portion of the slave trade saw ~15% mortality, though that would have been high for non-slave passenger travel.

https://en.wikipedia.org/wiki/Middle_Passage

Deaths at sea definitely occurred. Credible accurate records don't seem to be available however, as this article's abstract notes:

Farley Grubb, "Morbidity and Mortality on the North Atlantic Passage: Eighteenth-Century German Immigration" (1987). https://www.jstor.org/stable/204611

[AnIdiotOnTheNet]

Yeah, the only kind of boat where that was probably true was the kind where the majority of "passengers" definitely weren't going willingly.

[inglor_cz]

"Coffin ships" that carried the Irish fleeing the potato famine to America were notorious for their death rate and generally bad conditions. Of course, this was an already weakened population of passengers.