WordNet (r) 3.0 (2006):

sink in
    v 1: become clear or enter one's consciousness or emotions; "It
         dawned on him that she had betrayed him"; "she was
         penetrated with sorrow" [syn: click, get through,
         dawn, come home, get across, sink in, penetrate,
         fall into place]
    2: pass through; "Water permeates sand easily" [syn:
       percolate, sink in, permeate, filter]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "sink in":
   affect, arrest the thoughts, be glimpsed, be remembered, bemire,
   bog, bog down, catch the thoughts, come home to, come through,
   dawn on, get across, get over, grab, hit, hit the mark, impress,
   impress forcibly, make an impression, mire, never be forgotten,
   obsess, penetrate, rankle, register, rock, smite, soak in, stodge,
   strike, strike hard, strike home, tell, traumatize