Cruising the Baltic Sea
The Baltic Sea is a brackish inland sea bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. While brackish this salt content is fairly low at the surface and swimming pools on board ships should be much more pleasant to swim in than those cruising the open ocean.
The idea of cruising is to visit places and this Sea provides connections to many interesting places. The following countries have outlets on the Baltic Sea (moving clockwise)
Much of the Baltic sea ices over in the winter so cruises are limited to the summer season.
On Shipboard, the air temperature is dominated by the sea temperature which, in turn, depends on the melting of the Winter accumulation of ice each spring. However, by July air temperatures will reach 16 or 17 deg C (61-63 F) rising to 22 deg (72 F) near mainland coasts.
As soon as the ice melts the sea temperature rises rapidly in late Spring and early Summer. For example the Danish islands and in the Southern Baltic near Kaliningrad will only reach 10 or 11 deg C (50-52 F) in May but will rise to 17 to 18 (63-64 F) by August. To the south of Gotland the May temperatures of 5 or 6 (41-43) will become about 16 degrees (61 F) in August. Even in the Gulf of Finland were the May temperature averages of just 1 deg C (34 F) rises to 16 (61 F) or higher approaching St Petersburg in August. The day time temperatures over land can be as high as 30 deg C (86 F) on occasion but will normally be in the mid to lower 20's.
Thunderstorms can strike the area at any time of the year but the late Spring and Summer months (from May to August) will typically have from 2 to 3 thunderstorms per month at Copenhagen and Stockholm rising to 4 or 5 towards the east near Riga, St Petersburg and Helsinki.
Cruising the sea itself
The Baltic Sea is a large body of water with several bays but is relatively isolated from the ocean. Thus the tides are minimal and the surface fairly smooth in the absence of an actual storm. Cruising this overgrown lake should be a pleasant and smooth experience most of the time.
Cruise Ships frequent these waters with tours that last 10 to 14 days depending on what countries you want to visit. Typically no cruise will reach all of the countries so you have to be choosy. Often one ship will travel the Baltic Sea alternating between a clockwise and counterclockwise traversal of the sea. Some sea days (days without docking) are to be expected.
Somewhat longer cruises may venture out into the North Sea. And North Sea cruises may also sample a few spots in the Baltic. Most cruises will only stop at a few of the available ports so be sure and study the itinerary to determine which sites are featured.
Most of the distinct Baltic Cruises feature an extended stay in St. Petersburg. This means you can visit the historic city for a couple of full days while returning and sleeping on the ship at night.
Some cruises feature Berlin in the brochures. As you can see from the map above Berlin is no where near the Sea and a visit to the city is not included in the price of the cruise. A shore excursion to Berlin will typically cost more that $200 and will take 3 to 3 1/2 hours to reach the city. Travel can be by bus or rail. The cruise ship accommodates this long travel time by arriving early and leaving late. Even with the 6 or 7 hours travel time you will likely still have 7 or 8 hours in the city. Of course, a shore excursion is optional and you can enjoy the local fishing village or not even leave the ship if you prefer.