The Royal Canal Tour starts up on April 4th and runs daily from then on (until next winter). This is a shorter tour (50 minutes) around the island of Djurgården which is a National City Park and where many tourist attractions are located... like the Vasa Museum, Skansen, ABBA the Museum and much more. Earlier blog article.
The Under the Bridges Tour starts up on April 11th... at first just on Fridays, Saturdays, Sundays and holidays until the last week of April when it starts to run daily. At an hour and 50 minutes long, this is a more comprehensive sightseeing tour and takes you past all 14 islands, under 15 bridges and through 2 locks. A great way to get a good overview of the city! Earlier blog article.