Sea legs was a divine magic spell that could give a creature the ability to keep its balance and maneuver on board a vessel being tossed by waves. The reverse of this spell, called land legs, removed this ability, making it difficult and possibly dangerous to attempt any action on a heaving deck. As a healing effect, sea legs also prevented sea sickness.
In order to cast this spell, the priest had to touch the person or creature being targeted. The effects lasted an hour for every level the priest had achieved. Sea legs gave a person or creature the sense of balance that normally required years of sailing experience to develop, such that they could move about on a vessel in high seas and not be subject to sea sickness. If cast in reverse, land legs caused the target to lose this ability such that all movements and actions could result in being knocked off their feet. and made it difficult to stand back up.