They use to sell the blue ring octopi at a aquarium store here. You had to sign a release that you are aware of how deadly they are and take full responsibility if your pet kills you in order to buy one.
And the first life I ever saved was a man stung by a stone fish in his aquarium. Luckily I was working the ER that day after school because the doctors did not have a clue how to treat him. But I took up scuba diving when I was 11 and we had to learn marine poisons as part of our training. It's amazing what people keep as pets.
What would worry me most in the water over there are the box jellyfish. I have seen what they can do. If you somehow manage to survive you will wish you did not!!!