To come to Berlin, I mean.

Finns are the happiest people on Earth, I’m told. Germans, well, aren’t. And Berliners erst recht nicht (certainly not).
Traveling from Berlin to Helsinki — without using a plane. Flying is a major CO2 emitter when traveling. But how feasible are alternative modes of transportation?
Maybe it would be faster to take the ferry Helsinki to Rostock Then the train to Berlin from Rostok?
Yeah. Years ago I took the Finnjet ferry from Travemünde to Helsinki (twenty plus hours).