This is an unguent that is exceptionally buoyant. When spread on an object, it increases the object's buoyancy drastically. The unguent from a single potion vial is capable of compensating for as much as 600 pounds of non-buoyant weight.
This material quickly breaks down, and loses its potency after approximately three hours. It's also important to note that this material is buoyant while in the potion bottle as well, and may hinder the swimming actions of the creature in possession of an unused potion.