The present invention relates to a foldable cover (1) for a swimming pool (100). The cover comprises a foldable cover material (2), a number of supports (3) extending over the cover material for folding and unfolding the cover material and two support units (10) to be arranged on opposite sides of the cover (1) for rotatable attachment of outer ends of a number of the supports (3) around first rotation axes. The support units comprise attaching means for attaching the support units to the swimming pool. The attaching means comprise suspension arms, which suspension arms are provided with first suspension means for releasably suspending the support unit (10) on a rail (101) of the swimming pool (100).