Why is a cruise ship anchored off Navy Pier?

CHICAGO (WLS) -- It's a rare sight on Chicago's lakefront - a cruise ship anchored in the water just off Navy Pier.

The M.S. Hamburg, a German cruise ship, made a stop in Chicago on Tuesday. It has 400 passengers on board and made the voyage from Milwaukee on Tuesday morning.

The cruise originated in Montreal as part of a multi-day tour of the Great Lakes.