Abstract: A mooring system (10) for use in mooring a marine device (24) within a fluid (12) subject to flow comprises a mooring line (16) to be secured to an anchor (18) and defining a tether point for a marine device (24), and a loading assembly (20) secured to the mooring line (16) and configured to generate hydrodynamic lift when exposed to flow to apply tension to the mooring line (16). In embodiments of the invention the loading assembly (20) is configured to also generate a buoyancy force, such that tension is applied to the mooring line (16) by a combination of the hydrodynamic lift force and the buoyancy force.