Clarity: This is the most common opposite and applies to both literal and figurative meanings.
Examples:
* Literal: Murky water vs. clear water
* Figurative: Murky situation vs. clear understanding
Other options:
* Bright: Can be used for literal light or figurative brightness
* Clean: Emphasizes purity or lack of sediment
* Transparent: Specifically implies visibility through something
* Lucid: Used for clarity of thought or expression
* Distinct: Refers to a clear separation or distinction
It's important to consider the specific meaning of "murky" in the context to choose the best opposite.