When you put cork into a cup of water (fresh or salt), you will see that the cork will float. However, the cork will float on the surface of the salt water, but it will slightly submerged in the fresh water. See image here

This is because the density of the salt water is higher than the density of the fresh water, meaning that the salt water weighs more than the fresh water.

The cork weighs less than both the fresh water and salt water, which is why it will float in both solutions.

The difference in the density between the cork and water is greater when using the salt water compared to the fresh water, which is calculated below. The tendency of an object to float in a liquid is called buoyancy, and the cork is more buoyant in the salt water. You can also test this using your body to float in a pool or lake (fresh water), then floating in the ocean (salt water). You will see that your body is also more buoyant in salt water.

DensityCork = 0.24,
DensityFresh Water = 1.00,
DensitySalt Water = 1.05,
Difference in density (DensityFresh Water – DensityCork) = 0.76 (Less Buoyant)
Difference in density (DensitySalt Water – DensityCork) = 0.81 (More Buoyant)