Ice can vary widely. The ice typically found at bars is larger, clearer and denser than the average freezer-made crescent cube. Since the bar ice cube is larger, it has less surface area exposed to the drink (and so melts slower), compared to using lots of smaller cubes (cumulatively a larger surface area of ice melt) to achieve the same level of chilling. By this reasoning, you’d think using lots of little cubes would be the best bet for a quickly chilled drink. However, more surface area equals more ice-melt and it is the water on the ice that actually over-dilutes your cocktails.
Why is cloudy ice “bad” ice? Because cloudy ice indicates the impurities in your water have been trapped inside the cube from rapid-chilling the water to create ice in your freezer. Cloudy ice is also more prone to shattering and those tiny ice shards tend to over-dilute your drink.
Adjust your shaking times depending on the ice you are using to craft your drink, as your level of dilution will adjust vary. This is why straw testing (tasting your drink before serving) is recommended on all cocktails.