Abstract: A fin for swimming and underwater activities includes at least one foot pocket configured to accommodate the foot of a user and at least one blade associated rigidly with the foot pocket. The fin further includes a substantially spherical joint interposed between the blade and the foot pocket. An upper portion of the joint is rigidly coupled to the base of the foot pocket; and a lower portion of the joint is rigidly coupled to the blade in a portion that is proximate to a respective first end. The joint is lockable in a plurality of different configurations and introduces at least two degrees of rotational freedom.