An Amphibious unit may enter underwater provinces without penalty.
Poor Amphibians may also enter, but will receive penalties to their attributes: -3 attack and defense skill, +1 Encumbrance, Combat Speed halved. Some units, notably s and other Mermen, will be marked as poor amphibians in their land shape but transform into full amphibians when moving underwater.
Both types can swim over rivers.
See also: Aquatic.