(3) Sea Level
No need to break out the fancy gear for this hike, Shmoopers. Though long, and written way before any of us were born, the poem is relatively clear and straightforward. Coleridge wanted it to seem conversational, rather than something that would require the use of a dictionary and tons of patience. So, despite being considered a classic, there's only one allusion and few uses of symbolism or other kinds of poetic wordplay.
In fact, it's practically a walk in the park (er, grove).