I’m reluctant to give you a mark out of 25 without being familiar with the specific marking criteria, but I can gladly offer you some feedback which, hopefully, you will find constructive.
In your response, you do lots of things very well. You engage with the set question, you use well-chosen quotations to support your points, and you also analyze different language techniques from those quotations. Your language analysis is also clearly explained and helpful, and you engage well with the ideas behind the text.
There are, however, some areas in which you might improve your work further. Your written expression in places might be more accurate, and your vocabulary more precise. For example, you write that the repetition of the word “far” emphasizes the depth and also the abysmal quality of the sea. This, so far, is good. However, you then write that this repetition has “negative connotations may imply that something bad is about to happen.” There is a connective missing between the words “connotations” and “may.” This part of the sentence should read, “negative connotations which may imply.” There are a few errors like this in your essay, which might easily be corrected with a more careful or more thorough proof-reading.
In the same part of the essay, you use the word “bad.” This word is rather broad and vague. It has many possible meanings and doesn’t necessarily demonstrate that you have a precise understanding of the meaning of the poem. If you can use a more precise word, this would help you to demonstrate that you have a precise, rather than vague, understanding of the poem. For example, perhaps you might replace the word “bad” with “dangerous,” “terrible,” or “devastating,” depending on which word best fits your own interpretation of the poem. You might also find it beneficial to re-read your essay, see which other words in your interpretations are a little vague, and replace them with more specific, precise words.
A second way in which I think you might improve your response is by focusing more often on key individual words from the quotations you use. For example, you have quoted the line: “battening upon huge sea worms in his sleep.” From this quotation, you might have singled out the word “worms” and written about the connotations of that word. Many people associate worms with death, owing to the fact that worms eat dead bodies. Worms, for most people, probably also connote dirt and unpleasantness. These interpretations of the word “worms” add to the interpretation of the overall image. The image becomes more visceral, more repellent, and more disturbing. Generally, it is a good idea to focus in on individual words like this, as it is a good way of demonstrating that you are able to understand the writer’s word choices to a very forensic, perceptive degree.
I hope you’ve found at least some of this feedback helpful, and I wish you good luck with your future essays.