"Falls" implies an accident; "jumps" does not
Interested in Language
As everyone ought to do who falls into deep water in their clothes.
It means they wear their clothes and jumped into the water?
Were they wearing the clothes that fall into deep water?
The person was wearing clothes. The clothed person fell into the water by accident.
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.
Your quote is a fragment, not a whole sentence.