Welcome to TONMO, the premier cephalopod interest community. Founded in 2000, we have built a large community of experts, hobbyists and enthusiasts, some of whom come together when we host our biennial conference. To join in on the fun, sign up - it's free! You can also become a Supporter for just $50/year to remove all ads and enjoy other perks, like Site Search. Follow us on Twitter or Facebook for more cephy goodness.
From the appearance of white spots on the arms, and arms apparently longer from arms 1 (front arms) to arms 4 (back), I'd say it is one of the "Octopus macropus" group of species (genus Pinnoctopus according to Steve O'Shea, 1999: NIWA Biodiversity Memoirs112) but I can't say which species it might be. See if you can identify it yourself from the FAO Guide (Vol. 3: http://www.fao.org/3/a-i3489e.pdf under "Callistoctopus"). The size is difficult to gauge but it looks big enough to be mature, which would make it an adult.