these signs tend to be more in tune with currents - more effected by their environment. Hence, they can be sensitive, intuitive, emotional, feeling and receptive. They can also be self-indulgent, self-pitying and indecisive.
if we were to look at these three signs as the various forms of water, Cancer is liquid, Scorpio is solid, and Pisces is gas. maybe. but some scorpios i have known to be icy, but also quite hot! and i've held some pisces flesh to be sure.
these folks are deep, or shallow!
for some water insights, you might try heavy water, composed online by a cancer - magdalena donea.