Answer: don't. We had the interesting experience yesterday of catching two large octopus while bottom-fishing for flathead. Jamie failed to quite get his on the boat, I called for a net the moment I saw mine... and it was easy to see, with tentacles more than yard long (at my chest, the tentacles still touched the ground). I then had to kill it -something I'd done often with the small occys we caught in SA. In the gills, grab,snap and it's over... only it wasn't. The Occy was LEAVING. Now. as fast as possible with eight arms in turbo... I grabbed it and dropped it in a tall bucket, assuming death had happened and this was just autonomous reaction. There followed a period of helpless laughter from my friends(and 'where is the video camera when you need one') as Dave tried to keep the Occy in the bucket... Tentacle with suckers the size of dollar coins comes schlurping up the side, Dave detaches it, plop, plop, plop, plop... and drops it into the bucket... As the next comes out. Plop, plop, plop, plop. repeat... faster and faster. It was like a sort of octopus game of whack a mole. Eventually Jamie came to my rescue and cut the entire head off, which worked a lot better and faster.
It seemed to be a cephalopod day. Our new fisherman was hauling up his second or so flathead... and found he had a squid clinging on to the flathead. Not hooked, just that determined to eat flathead... it came off into the fish-box and attacked a packet of nachos that someone had dropped in there in their haste. The photo-opportunity of a lifetime... 10 tentacles wrapped around the packet, and biting holes in it. Flathead and chips for an arrow-squid.
Anyway, a day of different seafood... finished with Peter turning Jamie green with a little squid sushi. (Peter ate a piece, I proved I could, so did our newcomer, and then Jamie thought well... if we could, he could. No, no-one was forcing him, or even saying go-on. I've done it before, Peter likes it, and the new fellow had made a foolish comment (If you eat it raw I will). heh. hasty eating of remaining nachos followed.)
The tide was too far out for us to come in easily, so we stopped, cleaned fish, and and then went in on the auxillary... which cooked :-(. Should have put the squid on it.