Which marine mammal has tusks in both males and females?

The walrus is the marine mammal in which both males and females have tusks.

Walrus tusks are elongated upper canine teeth that continue growing throughout life. They can be used for fighting, displaying dominance, helping animals haul themselves onto sea ice, and creating breathing holes in ice. Both sexes possess them, although males generally develop longer and thicker tusks.

Walruses live in Arctic and sub-Arctic waters and are divided into Atlantic and Pacific populations, with a separate Laptev Sea population often recognized. Their sensitive whiskers help them locate clams and other invertebrates on the seafloor, which they commonly uncover by disturbing sediment with their snouts.

Narwhal tusks are also enlarged teeth, but narwhals are different from walruses and usually show the prominent tusk mainly in males. Elephant seals have enlarged noses, not tusks.