The Collaborative International Dictionary of English v.0.48:

Sea cock \Sea" cock`\
   1. In a steamship, a cock or valve close to the vessel's
      side, for closing a pipe which communicates with the sea.
      [1913 Webster]

   2. (Zool.)
      (a) The black-bellied plover.
      (b) A gurnard, as the European red gurnard (Trigla
          pini).
          [1913 Webster]