What do they look like? The body of a blue whale is a maximum of 98 feet (30 m) long in the southern hemisphere and 89 feet (27 m) in the northern hemisphere. Adult blue whales weigh approximately 360,000 lbs. (160 tons), equal to about 23 adult ele-phants.he coloration of a blue whale is blue-grey with lighter gray mottling on a darker background, like dark marble. The variation in color patterns between whales helps identify individuals. The underside of the flippers may be light colored or white, and the underside of the fluke is dark.