...to your whisky:
[A]dding water releases molecules that improve the flavor. Water and ethanol don’t make for a perfectly uniform mixture. Aromatic compounds could become trapped in ethanol clusters and never reach the surface. Our tongues are only capable of identifying the flavors, sweet, salty, sour, bitter, and umami (savory), so aroma is really important for detecting all the other flavors that connoisseurs appreciate in whiskey.
Guaiacol is what gives whiskey that smoky, spicy, peaty flavor. Chemically, guaiacol is similar to a lot of other whiskey aroma compounds like vanillin (with the scent of vanilla) and limonene (citrus). These and other flavor compounds are not attracted to water and are more likely to become trapped in ethanol clusters.
So, just add a couple of drops to your dram, especially if it's cask-strength. But start with good whisky; diluting crap won't improve it.