What does all in the same boat mean
Welcome to Using English.
There is a great resource of idioms here on the site.
In the same boat - Idiom Definition - UsingEnglish.com - here is the one you asked about.
From this page, English Language Reference Resources - UsingEnglish.com, you can enter a word like "boat" into the idiom section.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.