Humans may not be on the preferred menu, but they're sure as hell a form of food and in times of scarcity the menu becomes flexible.
It's interesting that he was able to develop a close relationship with an octopus, but the romanticized crap about sharks seems both unnecessary and flawed.
Seems that the author is speaking from a position of many years of experience in observing wildlife and a full year+ diving with these creatures every day.
Moreover, it's quite a solid point that if the sharks actually saw us as an 'on the menu' food source, there would be attacks more than daily. The general take from shark experts I've read seems to be that they are generally mistaking us for seals on occasion. For example, on Cape Cod in Massachusetts, seals have started to increase in population, and shark incidents with swimmers/surfers have also increased.
My issue is he's making generalized statements about sharks based on years of diving in a specific region: the icy waters of cape town.
It seems perfectly obvious to me that his observation can equally be explained as "the sharks in the icy waters of cape town may be generally well-fed".
Frankly the article is nothing more than a thinly veiled advertisement for a book, and probably lacked substance if it stayed purely on-topic regarding the octopus. I expect the book to suffer similarly.
So how do they desperately fail at differentiating us humans from seals?