An improved submersible mollusc farm is disclosed. A line of cables bearing the culture ropes and the cylindrical buoys which maintain the line horizontal is suspended from end floats. The end floats include a filling/emptying system using water by way of ballast, in order to raise or submerge the line by inflating the end floats with air. Submerged tension buoys are connected to the end floats by tension cables and pulleys which are fixed to the dead weights provided at either end of the line. The vertical thrust of the tension buoys causes the pulley to stretch the cable and tauten the line.