On the other end of the scale, the giant Australian cuttlefish weighs up to 22 pounds and measures about 1.5 feet long. Both cuttlefish and squid are a bit wild-eyed—but in different ways.

Scientists know very little about the elusive giant squid, which lives at ocean depths of between 300 and 1000m or more. Much of what they do know comes from the remains of dead or dying specimens ...