The Collaborative International Dictionary of English v.0.48:

Seascape \Sea"scape\, n. [Cf. Landscape.]
   A picture representing a scene at sea. Compare landscape.
   --Thackeray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

seascape
    n 1: a view of the sea
    2: a painting of the sea (as distinguished from a landscape)
       [syn: seascape, waterscape]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "seascape":
   airscape, cityscape, cloudscape, diorama, exterior, farmscape,
   interior, landscape, lookout, outlook, panorama, pastoral,
   perspective, prospect, riverscape, scape, scene, scenery,
   scenic view, seapiece, sight, skyscape, snowscape, sweep,
   townscape, view, vista, waterscape