The Collaborative International Dictionary of English v.0.48:

Scull \Scull\, v. t. [imp. & p. p. Sculled; p. pr. & vb. n.
   Sculling.] (Naut.)
   To impel (a boat) with a pair of sculls, or with a single
   scull or oar worked over the stern obliquely from side to
   side.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sculling
    n 1: rowing by a single oarsman in a racing shell