Rinse the octopus. Bring a large pot with 2 liters of water, vinegar and 1 tablespoon of salt to a boil. Reduce to low, add the octopus, partially cover and simmer until fork-tender, about 1 hour.
Peel and thinly slice the garlic. Rinse the herbs, pluck and finely chop. In a bowl, stir together the garlic, lemon juice and oil, season with salt and pepper.
Cut the octopus legs into small pieces and add to the bowl, tossing to coat. Refrigerate 2 hours, season to taste and serve.