Question

Which is the largest existing mammal?

Answer 1

Hint:This mammal lives in the sea or in the ocean and the mammal looks blue under deep water but when it comes on the water surface it appears blue-grey.

Complete answer:
Blue whales are the largest animals that exist on Earth. These marine mammals are ruling the oceans which are up to 100 feet long and weigh nearly 200 tons. The tongue of the blue whale solely will weigh as much as an elephant and their heart will weigh as much as an automobile.
Diet: Blue whales consume tiny shrimplike animals known as krill. At certain times in the year, a single adult blue whale can consume nearly 4 tons of krill per day. The giant animals will first feed itself by first gulping a mouthful of water, and will expand the pleated skin on their throat, as well as the belly to take it in. The whale’s massive tongue will force the water out through the thin, overlapping baleen plates. Thousands of krill are and then swallowed. 
The calves of the whales are the planet's largest creatures. About one year after inside its mother's womb, the baby blue whale will weigh up to 3 tons and stretch to about 25 feet. It will feed only on the mother's milk and will gain about 200 pounds every day for its first year.

Note: During the 1900s the whalers were hunting the whales to obtain whale oil and thus, they were driving near extinction. Thus, in 1966, the International whaling commission was formed to protect them.