Nahum asks this rhetorical question to emphasize the negative answer that it anticipates. Alternate translation: "you are not better than Thebes ... wall." (See: [[rc://en/ta/man/translate/figs-rquestion]])
These two phrases share similar meanings. The word "sea" refers to the Nile River, which ran near the city. Nahum speaks of the Nile as if it were the wall that protected the city. Alternate translation: "which had the Nile river as its defense, as some cities have a wall for their defense" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-parallelism]])
# rampart
A rampart is a wall built around a city to keep enemy armies from getting into the city.