yeh but! he said that there about 100kg to save, he still has 20litres.120l is actually 120 kilos!
The density of any substance is the mass (in kg) of the substance posessed by unit volume( 1 cubic meter) of the substance. The Density of Water is approximately 1000Kg/m3. Hence converted in litre, density of water becomes 1 Kg/Litre.