edit the following sentence with pronoun case:"the shower of sinking bricks caused he and his diving partner to race away from the collapsing seawell."

Would you say any of the following?

~~ I really like he.
~~ She gave her book to he.
~~ The batter unintentionally hit he with a fly ball.

Of course not. What would you substitute for "he" in each of these sentences? Do the same with your sentence above.

And I'm sure you mean "seawall" instead of "seawell," right?

you would say none of them because, they don't sound right ... don't you think?

Exactly.

And why don't they "sound right"? Because you are used to hearing people use "he" for subjects and "him" for objects.

Now ... how does that transfer into the sentence in the first post?

To edit the sentence with the correct pronoun case, replace "he" with "him":

"The shower of sinking bricks caused him and his diving partner to race away from the collapsing seawell."

To determine the correct pronoun case in sentences like this, it is helpful to break down the sentence and identify the function of the pronoun. In this case, the pronoun is the object of the verb "caused," so it should be in the objective case, which is "him" instead of "he."