I've gotta say, the Humboldt squid are pretty nasty! They certainly are beautiful and interesting animals but they are the biggest fear for divers in the area (I live in Northern Humboldt). They get pretty darn big and are usual in groups; I've had friends who are divers talk about having to come up early just because they could see groups further away in the water just heading their direction.
i think the line between aggression and enthusiastic curiosity is a fuzzy one at best for any animal, not to mention humbolts. since squid use their tentacles to examine things as well as attack, you cant really rule out that the squid was just trying to find out what the big scary soulless metal thing was doing in his backyard.