No, because nobody talks about the “north coast.”

Yes, the great lakes are usually included as coasts (when not included, their exclusion is typically explicitly noted.)

Exactly. I got downvoted unfortunately, which means that at least someone thought it was a ridiculous question. It's not.

Navigable Waters of the United States has a specific legal definition [1] and it has nothing to do with whether it's salt water or fresh water. So the question of whether a particular state is "coastal" based on proximity to salt water a valid question!

[1] https://www.law.cornell.edu/cfr/text/33/2.36