The Steller manatee, also known as the giant dugong, is an extinct species of manatee, first described by German naturalist Georg Wilhelm Steller in 1741. This giant marine mammal once lived near the Command Islands in the Bering Sea, mainly distributed in the waters between Alaska and Russia. Due to its slow movement and fearlessness of humans, the Stella manatee was overhunted within 27 years of its discovery and eventually became extinct in 1768.

Dugong is a mammal of the genus Dugong in the family Dugongaceae of the order Manatees. Dugongs are whale like in shape, spindle shaped, and have a plump and round body; No obvious neck, small eyes, no dorsal fin, fin limbs thoracic fin like; The body is composed entirely of thick flesh and skin; Back dark gray; The whole body has sparse and soft short hair. Male incisors are slightly exposed. Dugongs are also known as "mermaids" because they use their forelimbs to embrace their young while breastfeeding, with their head and chest exposed to the water, resembling humans swimming in the water. Group activity, slow movement, gentle temperament, poor vision, sensitive hearing, usually in a drowsy state, sensitive to cold, prone to pneumonia and death. Dugongs feed on juicy aquatic plants such as seaweed and aquatic plants.