This is actually not a boat in action anymore, but in fact a restaurant! The s/s Norrtälje is now a well-known and popular restaurant with lunch offers and dinners (quite a few local dishes) but as I never ate there, it will have to illustrate the style of boat that can take you to Norrtälje. Her name is s/s Blidösund after a strait in the waters outside, and you can go on a six hour cruise from Stockholm on Friday evenings in summer which is a marvellous experience since you have daylight well into the late evening.
There is no problem to ride a bus in Norrtälje. There are several busses you can take.
This bus 969 even goes to KÄRLEKSUDDEN, a beautiful beach in Norrtälje look at my oter pages of Norrtälje.