How Long to Cook Octopus When Boiling It
To get the right consistency, cook octopus for 45 minutes to an hour, but keep the pot at a simmer, not a full boil. Start by bringing a large pot of water to a boil, then add the octopus and immediately reduce the heat. If the octopus cooks too quickly, it may come out rubbery, so don't try to rush it.
To check that your octopus is done, try sliding a knife into the thickest part of one of the tentacles. If it goes in smoothly with little resistance, your octopus is done.