Just spent a week in Manihi (350 miles north, northeast of Tahiti) which is the Octopus cyanea capital of the world. At noon while saying goodbye to the dive operator, I watched two very, very large O. c. mating in no more than 3 inches of water. Several others were cruising the area. They had no fear and as the female was trying to escape from the male, I stepped in front of her path to see what she would do. She crawled up and between my legs and kept on her way.
Several years ago I suggested this atoll to Roger Hanlon as a great place to watch O. c. One of my former students built a black pearl farm there and O. c.s were every where. I even watched one kill an 18 inch green turtle. Roger took his group to Manihi and has published some of their research. I am happy to report that the octopus population is still thriving on Manihi.