As with many of Carson's work, the main theme of this important text is the way that nature plces humans in a dynamic relationship with it that we must respect and be aware of. Failure to acknowledge this implicit relationship and the cycle of nature of which we are a part would be to threaten not only the survival of nature, but therefore our own survival.
Through her focus on the history of the ocean and the incredible biodiversity that is contained within the waters of the sea, Carson again and again establishes the way in which there are so many important connections between our species and the ocean. There is a very delicate balance to our existence and how we relate with the oceans that form such a massive part of our setting, and tipping the balance one way too much would have catastrophic consequences. One sad example she gives of this is in the case of oceanic islands, such as the Hawaiian Islands. Carson shows how human interference in the delicate and fragile cycles of nature in these locations has actually resulted in the extinction of many species.