Used to catch them back in the 1950's while snorkling or scuba diving. We'd fill a squirt bottle with RV toilet tank chemical (the blue stuff), find an octopus den (like a dugout under a sewer outfall pipe with clam and crabshells strewn around the entrance), then squirt a cloud of the toilet chemical in the hole. Out would come a pi**ed off octopus. If he was small enough to keep, just grab him, stay clear of his beak, and haul him ashore.
1955 at Duwamish HeadOne time a critter started coming out and we began backing off. We were 15' away from the hole and he was still coming out, so we skedaddled. If he was 15' long all doubled up, he was 30' from tip to tip. Lotsa good chowder there, but if you invite him for supper, you might be the main course!
One diver caught a baby off Mukilteo. Ne was playing with the little guy, posing for pictures with it sitting on his shoulder. It bit him in a neck artery and he died from anaphylactic shock. He was allergic to octopus spit, I guess.
I have no idea how you'd angle for them, especially nowadays when the fish huggers think they're so cute. Good luck, though and, like squid, don't cook it too long. It'll turn into rubber bands. One minute in a pot of boiling water for skinned and ground-up octopus meat, then rinse in cold salt water. Best chowder you'll ever eat.