WordNet (r) 3.0 (2006):

seeable
    adj 1: capable of being seen; or open to easy view; "a visible
           object"; "visible stars"; "mountains visible in the
           distance"; "a visible change of expression"; "visible
           files" [syn: visible, seeable] [ant: invisible,
           unseeable]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "seeable":
   apparent, beholdable, clear, clear as crystal, crystal-clear,
   detectable, discernible, disclosed, distinct, evident, explicit,
   exposed, exposed to view, express, hanging out, in evidence,
   in full view, in plain sight, in view, indisputable, indubitable,
   insight, manifest, naked, noticeable, observable, obvious, ocular,
   open, open to view, open-and-shut, outcropping, palpable, patent,
   perceivable, perceptible, perspicuous, plain, plain as day,
   recognizable, revealed, self-evident, self-explaining,
   self-explanatory, showing, tangible, to be seen, unclouded,
   unconcealed, undisguised, unhidden, unmistakable, viewable,
   visible, visual, witnessable