From Helsinki to Reykjavik, you can fly a direct flight to Iceland Air for 3 hours 35 minutes on Mondays, Wednesdays, Fridays and Sundays. There are also many variants of flights with connections (Oslo, Stockholm, Copenhagen) Also to Iceland you can fly from Turku - though at least with one change and almost 7 hours in total on the way.

The option with the ferry is much longer - twice a week from Helsinki to Stogkolm follows the St.Peters Line ferry (16 hours en route), then from Stockholm by the Swedish Railways train to Gothenburg (3 hours), from where the Stena Line ferry to Frederikshavn (3 hour), then by the Danish Railways train through Hjørring to Hirtshals (about 1 hour), and from there the Smyril Line ferry through Torshavn (Faroe Islands) to Seydisfjordur (Iceland) for almost 50 hours. From here, buses with a transfer can come to Reykjavik somewhere in 13 hours.