Ok you doubting Thomases (and Sanahs and Cals), here's proof of the blue-ringed octopus (Hapalochlaena lunulata) yesterday, which we found at Pante Parigi.
Notice that the brilliant blue rings give away the animal's identity.
Blue-ringed octopuses carry tetrodotoxin, a potent neurotoxin that has no known antidote...making it quite a bummer if you get bitten by one of these, as happens every once in a while to people wading in shallow reefs.
Incidentally, this is the same poison that makes eating pufferfish a risky proposition. Several other marine organisms are also known to make use of this neurotoxin, both for self defence and as a predatory aid.
One interesting nugget of information to remember for trivia challenges...blue-ringed octopuses don't make tetrodotoxin. Bacteria contained in their salivary glands do.
Finally, just in case you doubters still don't believe me, here's another photo, with the octopus sitting on a rock...again with blue rings just to reemphasise the point.