Ferrys between St Petersburg and Helsinki, Stockholm and Tallin
There is a year round fast train between St Petersburg and Helsinki taking 4 hours and with reasonable scenery. You have to compare this when think about a ferry. Yes the ferry can be a nights accommodation.
You can make a mini crusie of the Baltics and have a few days at each port of call, this makes sense. Note that these services do not operate year round.
The time schedule is set out below. There are almost daily departures during the main season. If inetrsted contact us and we can see how a sailing would fit your other Russian arrangements planned with us.