The Collaborative International Dictionary of English v.0.48:

Swamp \Swamp\, v. t. [imp. & p. p. Swamped; p. pr. & vb. n.
   Swamping.]
   1. To plunge or sink into a swamp.
      [1913 Webster]

   2. (Naut.) To cause (a boat) to become filled with water; to
      capsize or sink by whelming with water.
      [1913 Webster]

   3. Fig.: To plunge into difficulties and perils; to
      overwhelm; to ruin; to wreck.
      [1913 Webster]

            The Whig majority of the house of Lords was swamped
            by the creation of twelve Tory peers. --J. R. Green.
      [1913 Webster]

            Having swamped himself in following the ignis fatuus
            of a theory.                          --Sir W.
                                                  Hamilton.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "swamped":
   afloat, aground, at flood, awash, bathed, castaway, deluged,
   dipped, drenched, dribbling, dripping, dripping wet, drowned,
   engulfed, flooded, foundered, grounded, high and dry, immersed,
   in spate, inflood, inundated, macerated, marooned, on the rocks,
   oozing, overflowed, overwhelmed, permeated, saturated, seeping,
   set fast, shipwrecked, soaked, soaking, soaking wet, soaky, sodden,
   soggy, sopping, sopping wet, soppy, soused, steeped, stranded,
   stuck, stuck fast, submerged, submersed, swept, washed,
   water-washed, waterlogged, watersoaked, weeping, weltering,
   whelmed, wrecked, wringing wet