Three endemic species found nowhere else on the planet. Galapagos penguins, the only penguin found north of the equator, Galapagos sea lions, the smallest species of sea lion, and black striped salemas. Schools upon schools of them. And maybe an ocean sunfish (Mola mola), the second heaviest bony fish in the world, weighing in at 247 - 2000 kg ( 545 - 4400 lbs).
A youtube video of diving Cape Marshall posted by Behind the Mask on 29 March 2018.