The blood vessels of a blue whale are so wide that an adult trout could swim through them. Baby seals are called “”weaners.”” At its peak, a growing blue whale gains between 200 and 300 pounds per day. If a walrus eats enough food, it can grow wider than its own length. A whale’s heart is as big as a compact car. The sperm whale’s eyeball is about as big as an orange. Dolphins can hear underwater sounds from as far away as 15 miles. How can you tell when a porpoise is searching for a mate? It swims upside down. A whale’s heart beats about once every six and a half seconds. Bottle-nosed whales can dive 3,000 feet in two minutes. The sperm whale’s brain weighs 20 pounds, the largest in the animal kingdom.