The sperm whale has set several records. It is the largest toothed whale and has the biggest mouth of all whales. It could even swallow a person whole. However, it is not dangerous to people because it is only interested in attacking squid, of which it consumes around 1.5 tonnes a day. Its brain weighs 9.5 kilograms and is thus the heaviest of all mammals. It navigates through the seas using echolocation. You can hear it whistling, squeaking, and groaning under water from several kilometres away.