The adjective deliquescent describes something that tends to absorb so much water from the air around it that it starts to become liquified itself.
This scientific term is perfect for describing a substance like salt, which tends to pull moisture into itself, as it's in the process of becoming soggy. If you ever leave a dish of salt on the kitchen counter on a humid day and watch as liquid begins to pool around it, you can say, "Wow, that salt is deliquescent." The Latin root is liquere, "to be liquid."