Stella Lines started the ferry connection between Saint-Petersburg and Helsinki. The service runs overnight between Morskoy vokzal terminal of Saint-Petersburg and Olympiaterminaali in Helsinki. The price is 50 € (60 € week-ends) one way and 85 € (100 € week-ends) two way without a cabin.
Did not try it yet, for me the bus is still the best option cause it departs several times a day (the ferry departs through a day, it’s only one ship now). However, the sea connection is back again and it’s good, hope it will be extended in the future.
P.S.: not much information in English actually and yet no online service comparable to Silja or Viking ones. Let’s see how this next try to establish sea connection will turn out.