Flexible pipes of thermoplastics such as polyethylene and polypropylene are excellently suited for the construction of submarine outfall systems because they can be extruded in long sections, towed fully equipped with anchoring weights to the outfall site from the production base, and sunk directly on to a seabed with a minimum of underwater work. When lying on the seabed they can yield to extreme wave and current forces and conform to the seabed when underscoured without failure. This factor allows a light structure, a short implementation time and a cost-effective outfall system.