Why are whales so big?

“As you enter the water, you start to lose heat from your body that you aren’t losing on land or air,” he explains. To counteract that constant loss of heat, humans use wet suits, whales have blubber, and otters have thick fur. “But really the easiest way to counteract it is to get bigger,” Gearty says. As bodies balloon, volume increases faster than surface area does, so you produce more heat in your body but lose comparatively less of it from your skin.

From Why Whales Got So Big