hazmatgerman (X) Nov 5, 2010:

There also is a fundamental difference in meaning between the two terms. Decommission removes the public service status but does not necessarily mean the vessel won't be used any more, though it often is broken up later. Lay-up means the private vessel is taken out of service, removed to an anchorage with a very small maintenance / guard crew and may be reactivated within months when the Baltex or others take up again.