What are the units of the specific gravity of water?

That is how specific gravity is defined.

737.22 - see http://www.simetric.co.uk/si_liquids.htmThe sp. gravity of the petrol(vehicle) is 0.73722 and that of natural petrol is 0,71122 Note that specific gravity has no units.

The SG of water is 1

The specific gravity of salt water is about 1.025 or so.

specific gravity = relative density ( relative to water), water is 1000 kg / cubic metre, say iron is 7800 kg / cubic metre, then relative density is:7800/1000 = 7.8, or 7.8 times the density of water