What is the strongest sea animal?
Pound for pound the great blue whale would be the strongest based on size and weight alone.
The elephant is the strongest land animal. The blue whale is probably the strongest sea animal. The strongest pound-for-pound animal anywhere in the world, on land or in the sea, is the Hercules Beetle. It can lift 850 times its own weight. That's the same as you walking up to an M-1 Abrams main battle tank and lifting it up over your head.
I am going to say you meant to ask What is the strongest animal in the world? In the sea: The title belongs to the blue whale On Land: The title belongs to the African Elephant Out of those two, it would be the blue whale If we're talking carnivores, it would either be the Polar Bear, Kodiak Bear, or the Siberian Tiger.