Walcott uses uses the metonym of vibrant and diverse sea life and correlates that to describe the layers blocking a rich history. He is imploring the reader to simply go forth and look past the imposed obscurity to find the vast collection of their treasured past, and not to look for it in the confides of another context such as religion.

This reminds me of the personification many explorers attribute to the Titanic; it emphasizes the tragedy of such an event. By being giving human characteristics ("whose drowned face sleeps with open eyes") the reader is allowed and encouraged to imagine someone brought down, trapped beneath the waves, helpless and silenced. In that context, I feel the author is using that as a metaphor for a person's story going untold, or silenced altogether.

"Slant", in this context, meaning to present something, in this case the "truth", from a certain point of view. Not as a definitive, end all, irrefutable fact. As your "truth" might contradict or conflict with that of another's. If you do not express your perspective in an open and "kind" manner, than others will remain "blind" to it.

"Riddle" being the question of life's meaning and our role to play in the world. To be sagacious is to be wise, intelligent, and to have a keen insight. This directly contradicts what we know: that we know nothing conclusively, hence why philosophers ask these questions. "Why are we here?" What's the meaning of all this?"

Cullen mirrors the never ending struggle of African-Americans to Greek Mythology characters Tantalus (who suffers from eternal thirst and hunger) and Sisyphus (who rolls a boulder up a mountain only to be set back down for all eternity).

Hughes shatters the illusion of there being any significant difference between "white" and "colored". He listens to the same music and dances in the same manner, has similar interests and tastes, and yet, he is made to feel separated from the others by some superficial distinction. Despite the fact that he is just as American as his instructor.