Since the beginning of time, man has waged constant battle against the illnesses that affect him. We have looked for solutions in land plants and animals, solutions that are now increasingly scarce, due to the deterioration of the natural environment. But we have continued to investigate in search of infallible remedies, remedies which are much more complicated to find but possibly more efficient against a type of illness that affects millions of people around the world - cancer. We dive down into the depths of the ocean to discover treasures of nature, animals that, once investigated, can provide us with the chemistry necessary to combat this illness that plagues humanity. We will see how products like ET-743, Aplidine or Kahalalide turn out to be powerful drugs, with innovative action mechanisms, bringing fresh hope to patients with certain types of up-to-now incurable cancer.