Marine biologist here: this is the giant pacific octopus, one of the largest species of octopus and cephalopod on earth! And while intimidating, and technically powerful enough to do so, most octopuses do not have reason or instinct to pull a grown adult into the water, as their natural diet is comprised of a very different prey of mollusks, crustaceans, and small fish. (And occasionally each-other) This guy was most likely just curious, as octopuses can have the mental capacity of a small child, making them one of the most intelligent animals in the world. And although yes, all octopuses are venomous to some extent, the potency of the giant pacific octopus, though painful, is not fatally dangerous to humans if treated properly, and is only inflicted through bite from their powerful beaks, which are rarely used on humans. it is also not typically aggressive to us, with only about 4 documented attacks on divers having been recorded in the past 25 years or more. As long as you are calm and careful, you will be ok. What an amazing experience. Protect your marine ecosystems so we can ensure a future for these incredible animals!