Well, I wouldnt not say "just like birds'...but, beautifully , like what they are. if a comparison is needed, maybe more like a tuba and one of those slightly varying string instruments, which can be so beautifully hypnotic.
A reminder that the oceans, as the skies, are not at all 'empty' but full and rich. At least, for now. As we change our view of them from not-us and therefore, not worthy of respect -an attitude which has us dumping our waste into both -they may remain so. And, because in the deepest sense, we are them, in that there is hope for us.