Silja Line and Viking Line operate massive cruise ship–style ferries daily between Stockholm and Helsinki, either for single journeys or round-trip, two-day cruises. St. Peter Line operates a ferry service between Stockholm and St. Petersburg, Russia, with stops in Tallinn, Estonia; and Helsinki, Finland, along the way.
Silja Line. 08/222140; www.tallinksilja.se.
St. Peter Line. 08/4597700; anastasia.stpeterline.com.
Strömma Kanalbolaget. 08/12004000; www.stromma.se.
Viking Line. 08/4524000; www.vikingline.se.