The Demoseals are a rare species of the Demoman category.
The Demoseals have heavily varying clothes, but there are currently no known clothes that every Demoseal wears besides a Seal Mask
They are extremely rarely found at beaches, never found inland, but found in big groups in Cold Climates, like 2Fortctica.
They are mostly found swimming in the deep ocean, attacking any other TF2nimal that threatens them or their family.
They weight a lot, and have strong attacks.
It was discovered that they have some sort of local hive minds.
It's special feature, however, is that they don't appear in the photos, which led to the popular joke on the internet that Demoseals are vampires.