I've always liked this poem and find it a stand-out as far as memorability is concerned. I read some poems and forget them quickly. This isn't one of them.
It's interesting to consider what makes poems memorable. I like the commentary in this regard, and note particularly that "it begs to be read aloud" and "has been set to music more than once".
I think it sticks in my mind mainly because of its musicality: the repetition, alliteration, and, most of all, the meter. It interweaves the ballad form beautifully with lines containing three pyrrhic/spondees and a trochee. I note that that 7-foot line-form is an extension of the 4/3 ballad foot structure, a structure that is foundational for song.
John
PS I cross-posted with Roger and agree with him as to content. But sometimes form is at least as important. As to other poems about the sea,
here is another of my favorites, again because of the musicality of its form more than its content.