A ship in harbour is safe, but that is not what ships are built for.

Related:

• A ship in harbour is safe, but that is not what ships are built for.
  William...
• A ship in harbor is safe -- but that is not what ships are for.
  John A....
• Ships don't come in ..
  they are built....
• Ships are safe in harbor,
  but they were never meant to stay there...
• What the hell--nobody said life was safe. --
  William...
• What do sea monsters eat?
  Fish and ships...
• Ship it
  ...
• And what have we got on this ship,
  a cuisanart?...
• Civilization is a movement, not a condition; it is a voyage,
  not a harbour. --...