Thirty lines cruise the Baltic during the spring, summer and early autumn. In 2012 the number of cruise visitors was 4.2 million.
Measured by calls, the main ports are Copenhagen, St Petersburg, Stockholm, Tallinn, Helsinki, Kiel, Oslo and Rostock. Numbers of visitors at the other ports are many times smaller.
Cruise passengers spend each night on the same ship, usually while it travels from one port to the next. It is also common for a number of days to be spent "relaxing at sea", meaning not in any port.
Sometimes the "turnaround port" — where a cruise begins and ends — is outside the area, such as the Netherlands or the United Kingdom.
Shorter cruises begin and end in the Baltic , so most passengers start their holiday by flying to the port. The busiest Baltic turnaround port is Copenhagen
How passengers spend their time is up to them. The cruise line will usually offer a range of excursions at each port of call but people who prefer to do something else can make their own arrangements.
The exception is St Petersburg, where westerners normally require a visa to go ashore but are exempted from this rule if they stay in the company of a licensed guide from an authorised tour company.
Except for Russia, all the countries with Baltic coastline are EU members. Western nationals, who make up the great majority of cruise passengers, can freely go ashore alone.
Even so, many passengers on standard cruises stay on organized excursions, if only because some ships berth rather far from the main sights, and chartered transport is the easiest way to get around.