* Heat Transfer: Water is a much better conductor of heat than oil. This means that heat from the surrounding environment will transfer to the ice cube more efficiently in water, causing it to melt faster.

* Density: Water is denser than oil. This means that there are more water molecules in contact with the ice cube, allowing for more efficient heat transfer and melting.

In simple terms, the water will "steal" heat from the ice cube more readily than the oil, causing the ice to melt quicker.