Visiting Tallinn 2nd till the 6th April, and would like to make a day trip to Helsinki by ferry. I've had a look online and Viking seem to be cheaper than Tallink or Lindaline. I'm just wondering whether it's cheaper to book now online for 30 euros return, or wait until we get there and book then. If its best to wait until we get there, where do we buy the tickets from? Hope you can help!