In Helsinki you can take a number of different boats that travel to Tallin, Estonia (a distance of 2.5 hours). We purchased economy class tickets, and expected to have designated seats, but these boats are more like commerce-bar-casinos than passenger ferry. The only seating available is located in the cafeteria, buffet restaurant, bar, higher-end bar, or nightclub. Private cabins are available but cost more. You'll also find an airport style shop and liquor store. Karaoke (Finns love karaoke), live music, and slot machines are provided for patron entertainment.
We noticed passengers carrying dolly carts and luggage, but weren't sure what they were for until the trip back where we saw each dolly loaded with cases of beer. Finns travel to Estonia because the alcohol is cheaper. Everything is cheaper in Estonia.
We saw a young man taking a nap using a package of meats for a pillow, old ladies wheeling around fully stocked shopping carts, an Englishman playing electric guitar over a karaoke backing track, retired couples dancing to a traditional Finnish band of 3 when there was suppose to be 4, and a drunken domestic dispute. To say the least, the party boat was an unsettling experience at 9am on a Monday, but on our return trip in the evening we got into the strange spectacle and tried to enjoyed ourselves. The boat ride is definitely worth it to spend the day in Estonia.