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]