Among marine creatures, the sea cow and sea lion are mammals, while the sea horse is a fish. 1. Sea Cow: The sea cow, a herbivorous marine mammal, resides in the Indian and Pacific Oceans, growing to 3m and weighing around 600kg. Sadly, it's vulnerable due to habitat degradation and hunting. 2. Sea Horse: The sea horse, a carnivorous marine fish, is found in shallow tropical waters. It grows to 35cm, weighs around 200g, and is vulnerable due to habitat damage and fishing. 3. Sea Lion: The sea lion, a carnivorous marine mammal, breeds on Pacific beaches. It grows to 2.5m, weighs around 350kg, and is Endangered.