For a day trip from Switzerland, the boat docks in Locarno and Ascona are the obvious places to board. There are several smaller towns in Switzerland where you can board as well, and many in Italy.
How to get to the boat dock
The boat terminal in Locarno can be reached from the train station in 3 minutes on foot. The dock is called 'Locarno NLM'. There is a parking garage at 2 minutes on foot.
Ascona can be reached by bus or by car. The boat dock 'Ascona NLM' is 5 minutes on foot from the bus stop 'Ascona, Centro'. Parking is also about 5 minutes from the dock.
Dates of operation
The boats on the Swiss part of the lake usually operate from late March to early October.
Tip: check the timetable before you start your trip.