[2] As of 2009, four ships service two routes under the Silja Line brand, transporting about three million passengers and 200,000 cars every year.

As a precursor to the policies later adopted by Silja Line, each of the three companies ordered a near-identical ship for Helsinki–Stockholm service to coincide with the 1952 Summer Olympics, held in Helsinki.

[10] The new company started out with used ships, which were not particularly well-fitted for the role they were meant for,[10] but in 1961 Silja took delivery of the new MS Skandia, the first purpose-built car-passenger ferry in the northern Baltic Sea.

[12][13] Despite the establishment of Silja, FÅA, Bore and Svea also continued to operate on the same routes with their own ships.

[15] FÅA, Bore and Svea soon realised that a similar arrangement would be preferable to their current fragmented image, and in 1970 a big change was carried out within the organisations: Silja Line was established as a joint marketing and coordination company between FÅA, Bore and Svea, and the ships of Siljavarustamo were divided between these three.

Already before the reorganisation Silja had ordered two new ships from Dubigeon-Normandie S.A. of Nantes to begin year-round service between Helsinki and Stockholm (until then the route was summers only).

[17] In Finland, and later in Sweden, a large maritime strike in spring 1980 stopped ferry traffic completely and prompted Effoa to terminate the Silja Cruises service.

[18] Despite the difficulties Silja's first real cruiseferries, Finlandia and MS Silvia Regina, entered service in 1981, which led to a 45% raise in passenger numbers.

Effoa had purchased the famously fast GTS Finnjet the previous year and from the beginning of 1987 the prestigious but unprofitable "Queen of the Baltic Sea" joined Silja Line's fleet.

[18] In late 1989, Wärtsilä Marine, the shipyard building Silja's new cruiseferries, went bankrupt, which led to the ships being delivered later than had been planned.

To ensure the delivery of their ferries Effoa and Johnson Line both purchased a part of the new Masa-Yards established to continue shipbuilding in Wärtsilä's former shipyards.

As a result, the seal's head logo replaced the colours of each individual owner company on the funnel.

In November, the new MS Silja Serenade made its maiden voyage from Helsinki to Stockholm, approximately seven months after the original planned delivery date.

[19] MS Sally Albatross was grounded outside Helsinki in spring 1994 and suffered major damage, which prompted Silja to give up traffic on her.

The Estonia sinking led to passenger numbers dropping, which did not help Silja's precarious financial situation.

[19] In 2000, the new owners brought one of their Super SeaCats into service on the Helsinki–Tallinn route and Neptun Maritime again changed its name, this time to Silja Oyj Abp.

However, Sea Containers' other operations were not as profitable and in late 2005 they announced their intent to give up their ferry division completely; this naturally including selling Silja Line.

In preparation for the sale, the unprofitable Finnjet and MS Silja Opera were taken out of service and transferred under Sea Containers' ownership.

As a result, Sea Containers, after barely a year before announcing their intention to give up the ferry business completely, continued operating them under the SuperSeaCat brand.

Finland Sweden Harri Hylje is Silja Line's seal mascot and the company's signature animal appearing in its logo.

A living Harri Hylje figure appears on Silja Line ships especially on weekends and on school holiday periods.

[29] At first the seal figure in the company's advertisements had multiple appearances: it swam along the ships, jumped in the water, sometimes even wore sunglasses and looked different depending on the artist in Finnish and Swedish marketing.

Citizens could play or take selfies with a remotely controlled Harri Hylje figure shown on a video screen.