The Collaborative International Dictionary of English v.0.48:

Thurrok \Thur"rok\, n. [AS. [thorn]urruc a boat.]
   The hold of a ship; a sink. [Obs.]
   [1913 Webster]

         Small drops of water that enter through a little
         crevice into the thurrok and into the bottom of a ship.
                                                  --Chaucer.
   [1913 Webster]