seaboat

from The Collaborative International Dictionary of English v.0.48

Seaboat \Sea"boat`\ [AS. s[=ae]b[=a]t.]
   1. A boat or vessel adapted to the open sea; hence, a vessel
      considered with reference to her power of resisting a
      storm, or maintaining herself in a heavy sea; as, a good
      sea boat.
      [1913 Webster]

   2. (Zool.) A chiton.
      [1913 Webster]