Gillwort

Gillwort is a kelp-like aquatic plant with a bitter taste. When chewed in a wad, gillwort allows those who normally cannot breathe water to do so, though after about thirty minutes the chew looses its effectiveness and the user must start a new wad. In addition a short-term immunity usually builds up, meaning that those who try to avoid otherwise expensive magical and more permanent solutions to water-breathing by simply shoveling gillwort into their mouths will find their aquatic breaths becoming shallower and shallower, even after only a couple hours. As a result, gillwort is primarily used by those who need only breathe water for short periods of time - merchants and quick-working deckhands being the primary users.