@David09 - Yeah, I did that experiment too. Actually the whole concept of specific gravity has a lot of practical applications.
For example, it can be used in a urine test. The specific gravity of urine can fluctuate based on the health of the patient. Abnormal results can indicate problems with the kidneys or even heart problems in a worst case scenario.
The urine test is not enough in and of itself to prove anything conclusively. But I think it’s a first start for many physical tests.