A rotary seal having first and second parts mobile relative to each other about a rotation axis. The first and second mobile parts each include an interface area having a plurality of protruding and recessed members with complementary shapes, the protruding and recessed members of one part engaging the protruding and recessed members of the other part in order to define decompression chambers with an increasing volume. The interface areas are located at a distance from each other without any friction between them.