Water, as they say, is the source of life. In astrology, Water signs are noted for their emotional and intuitive qualities; water being a flowing, malleable and soothing element. The Water signs are Cancer, Scorpio and Pisces. Stephen Arroyo has this to say of Water signs:

The Water signs are in touch with their feelings, in tune with nuances and subtleties that many others don’t even notice. The Water element represents the realm of deep emotion and feeling responses, ranging from compulsive passions to overwhelming fears to an all-encompassing acceptance and love of creation. The Water signs know instinctively that to realize their soul’s deepest yearnings, they must protect themselves from outside influences in order to assure themselves the inner calm necessary for deep reflection and subtlety of perception.

Water signs, in my experience, tend to be moody individuals, though not necessarily in a bad way. They are not the most optimistic of people (that’s reserved for the fiery Aries, Leo and Sagittarius) and are usually perceived to be supportive. My perception, however, is that this is true only if they do not feel threatened. Water signs retreat under attack, and hide behind their shell (Cancer), wait to act another day (Scorpio), or tell themselves the problem doesn’t exist (Pisces). Okay, so these are reductions, but since I’m ruled by impatient Mercury, I’m just looking for a shorthand. The trick is not to subject individuals to these reductions.

Air-borne Mercury, as mentioned in a previous post, is not at its most comfortable in these watery signs. Air bubbles through water and its freedom of movement is restricted. However, Mercury retrograding through Water signs can force the Winged Messenger to slow down and face up to things he’d much rather avoid; uncomfortable things like feelings, emotions, yearnings, that his rational mind tends to dismiss as woolly and self-indulgent.

References
Arroyo, Stephen. Chart Interpretation Handbook. Sebastopol, California: CRCS, 1989.