  Planets composed of large quantities of water that reside in the habitable
zone are expected to have distinct geophysics and geochemistry of their
surfaces and atmospheres. We explore these properties motivated by two key
questions: whether such planets could provide habitable conditions and whether
they exhibit discernable spectral features that distinguish a water-planet from
a rocky Earth-like planet. We show that the recently discovered planets
Kepler-62e and -62f are the first viable candidates for habitable zone
water-planet. We use these planets as test cases for discussing those
differences in detail. We generate atmospheric spectral models and find that
potentially habitable water-planets show a distinctive spectral fingerprint in
transit depending on their position in the habitable zone.
