Scientists are discovering that creatures from the ocean produce powerful substances that can help our immune system fight diseases like cancer and inflammation. These marine organisms—from tiny algae to sponges to fish—create natural compounds that can either boost or calm down our immune response depending on what we need. Several of these ocean-derived medicines are already approved for treating serious diseases, and many more are being tested in clinical trials. The ocean covers 70% of our planet and most of it remains unexplored, suggesting there are many more beneficial compounds waiting to be discovered.