The levelling work of rubbles as in case caison foundation for breakwater is still done by mainly the diver.
　The volume of the rubble levelling work is increasing every year.
　This report describes the field test with prototype levelling machine. The experiments were carried out on the two different water depths, ±0m and -12m.
　The sizes of rubbles are 5-20kg, 30-50kg, 50-200kg and the kind of rubbles are andesite.
　Our final purposes are to find out the levelling accuracy and officiency, mooring of floating crane, etc.
　From our test so far, the levelling accuracy is expected to be ±10-15cm for the above stones in under water execution by repeated levelling by using the levelling machine.