We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
I think there's a supposed to be a modifier for making an attack from a naval landing, but I don't remember if its the same sort as the strait crossing one. Are you sure the modifier you're seeing is related to the strait?
I don't think he's saying that there's an actual strait. He thinks that if you get off boats in port (rather than landing on the beaches, say) there ought to be no debuff at all.