Whitman uses apostrophe to address the sea. Apostrophe is a rhetorical figure of addressing an unreal, imaginary, abstract, or non-living object or phenomenon as if it were a living being. Most often, it goes with an exclamation "O", but this excerpt from "Song of Myself" shows an effective use of apostrophe without an exclamation.
The main purpose is that when Juliet wanted to be with romeo so romeo killed himself and Juliet drink poison hope this helps I hope you get it right :P