A hydraulic seal arrangement for a rotating machine comprises an annular housing disposed around a shaft having an axis of rotation, the annular housing being relatively rotatable with respect to the shaft and having a sealing fluid zone within a radially outer portion of an interior of the annular housing. A fin extends radially from the shaft into the annular housing, with at least a portion of the fin extending radially into the sealing fluid zone. In use, the sealing fluid is centrifugally accelerated before being directly introduced into the sealing fluid zone by a sealing fluid inlet so as to generate a swirl component upon its introduction.