The Collaborative International Dictionary of English v.0.48:

Submerge \Sub*merge"\, v. t. [imp. & p. p. Submerged; p. pr. &
   vb. n. Submerging.] [L. submergere, submersum; sub under +
   mergere to plunge: cf. F. submerger. See Merge.]
   1. To put under water; to plunge.
      [1913 Webster]

   2. To cover or overflow with water; to inundate; to flood; to
      drown.
      [1913 Webster]

            I would thou didst,
            So half my Egypt were submerged.      --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Submerge \Sub*merge"\, v. i.
   To plunge into water or other fluid; to be buried or covered,
   as by a fluid; to be merged; hence, to be completely
   included.
   [1913 Webster]

         Some say swallows submerge in ponds.     --Gent. Mag.
   [1913 Webster]

WordNet (r) 3.0 (2006):

submerge
    v 1: sink below the surface; go under or as if under water [syn:
         submerge, submerse]
    2: cover completely or make imperceptible; "I was drowned in
       work"; "The noise drowned out her speech" [syn: submerge,
       drown, overwhelm]
    3: put under water; "submerge your head completely" [syn:
       submerge, submerse]
    4: fill or cover completely, usually with water [syn:
       inundate, deluge, submerge]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "submerge":
   baptize, break water, bury, camouflage, cave, cave in, cloak,
   conceal, decline, deluge, descend, dip, dive, douse, drench, droop,
   drown, duck, dunk, engulf, float, flood, flood negative,
   flood the tanks, flop, flop down, flow on, flump, flump down,
   founder, give way, go below, go down, go under, hide, immerge,
   immerse, impregnate, inundate, lapse, lower, merge, obscure,
   overflow, overwhelm, plop, plop down, plummet, plump, plunge,
   plunge in water, pour on, rain, rig for diving, sag, saturate, set,
   settle, settle down, shroud, sink, sink down, slouch, sluice,
   slump, slump down, soak, sound, souse, submerse, subside, surface,
   swag, swamp, veil, wash, wet, whelm