The Collaborative International Dictionary of English v.0.48:

beachcomber \beachcomber\ [Written also beach-comber or beach
   comber.] (Naut.)
   1. A vagrant seaman, usually of low character, who loiters
      about seaports, particularly on the shores and islands of
      the Pacific Ocean.
      [Webster 1913 Suppl.]

            I was fortunate enough, however, to forgather with a
            Scotchman who was a beach-comber.     --F. T.
                                                  Bullen.
      [Webster 1913 Suppl.]

   2. a vagrant living on a beach.
      [WordNet 1.5]

   3. a person who searches along a beach for objects of value,
      such as lost objects or seashells.
      [PJC]

WordNet (r) 3.0 (2006):

beachcomber
    n 1: a vagrant living on a beach

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "beachcomber":
   Arab, Bowery bum, beach bum, beggar, beggarly fellow, blighter, bo,
   budmash, bum, bummer, caitiff, derelict, devil, dogie, drifter,
   drunkard, gamin, gamine, good-for-naught, good-for-nothing,
   guttersnipe, hobo, homeless waif, human wreck, idler, landloper,
   lazzarone, loafer, losel, lowlife, mauvais sujet, mean wretch,
   mucker, mudlark, no-good, pauvre diable, piker, pilgarlic,
   poor creature, poor devil, ragamuffin, ragman, ragpicker, rounder,
   sad case, sad sack, ski bum, skid-row bum, stiff, stray,
   street Arab, street urchin, sundowner, surf bum, swagman, swagsman,
   tatterdemalion, tennis bum, tramp, truant, turnpiker, urchin, vag,
   vagabond, vagrant, vaurien, waif, waifs and strays, wastrel,
   worthless fellow, wretch