According to wikipedia, octopus wrestling "involves a diver grappling with a large octopus in shallow water and dragging it to the surface."
Popular Mechanics (May 1966) provides some more details:
Two things work for the hunters. The octopus is basically timid, and divers work in teams. One man goes down (about 50 feet) and tries to force an octopus from his cave. When he comes up for air, the second man goes down and tries to pry the octopus loose from the rocks. If he's not up in 30 seconds, the third man goes down. They don't harm the animals. They just weigh them and throw them back in. Why do they do it? Well, why not?
There aren't that many people who seriously pursue art and wrestling at the same time, but Patrick O'Connor was one of them. Back in the 1940s, he was heavyweight wrestling champion of Ireland, but also had a Greenwich Village art studio. He was an artist of the "conservative Realist and Romantic school." Apparently he viewed art as his true passion. Wrestling was just a way to make money. From The Evening Independent, Sep. 9, 1944:
His portraits were too realistic. If a rich dowager had three chins, he refused to conveniently omit two of them. As a result there was no rush of customers, so the painter turned to wrestling as a means of earning an honest dollar.
Unfortunately I haven't been able to find any examples of his art, except for the ones that can be seen behind him in the pictures below. O'Connor is the one with the beard. The pictures were taken in his art studio.