TWIN SEA is a T-shaped floating pontoon used to moor two boats to one mooring while providing users with a boarding and landing stage. TWIN SEA also enables harbour masters to optimise mooring areas and provide customers with better facilities. TWIN SEA can, in fact, be used to double the capacity of a mooring area, to space out mooring buoys to facilitate navigation, or to combine the two. Mooring is also easier for users in relation to conventional buoys, as the pontoon is always in the eye of the wind and boats come alongside parallel to the pontoon. The material used (polyethylene) resists small bumps without damage. Boarding and landing with tenders is also made easier and safer. Users can reach and leave the pontoon using the specially-designed steps and, once on the pontoon, can easily and safety board their boat. The equipment rates highly in environmental performance. With two boats on one mooring, there is less damage to the sea bed and less visual pollution. The equipment is also reversible which means sites can regain their natural beauty in low season and can always been returned to their initial state. By doubling up the boats, the equipment can be used to free up the water and even the shore. The stem of each boat is moored to the left and right ends of the T. The pontoon and the two boats swing in the same way as one boat on a mooring buoy. TWIN SEA has been used for two years, both in summer and winter, in Britany (France), much to the satisfaction of sailors and harbour masters. As regards cost, for the same amount required to build 100 conventional marina moorings, TWIN SEA provides 2,000 moorings.