Rachel Carson wrote, "In nature nothing exists alone." So what's at the bottom of your ocean? Off the coast of California there are hundreds of thousands of barrels of toxic waste from the manufacture of DDT: Full LA Times Article: https://www.latimes.com/projects/la-coast-ddt-dumping-ground/ ; For more of the science behind the story, see the open access paper from Dr. Veronika Kivenson https://pubs.acs.org/doi/10.1021/acs.est.8b05859