I took the train back to Zürich, because I didn't have enough time for the boat trip back. Several commuter train lines run between Zürich and Rapperswil, thus you don't have to wait longer than 15 minutes before another train departs. The trip back to Zürich main station takes less than 40 minutes. Fares and rules of the ZVV network apply (see previous tip on boats).
The train ride is maybe not exactly as scenic as the boat ride, but for the variety it makes sense to alternate between them. With the trains you get closer to the small towns, the vineyards, and since it runs on slightly elevated route you have a pretty good view of the lake.
The most pleasant way to get to Rapperswil IMO - if you have enough time - is by boat. They depart from Zürich Bürkliplatz about every hour at minute :30 and take roughly 1:45 hrs. to Rapperswil with stops in major towns along the lake.
The cruise is very interesting, first with views of Zürich's old town, then the upscale residential areas along the "Gold Coast", later you see smaller or bigger towns, vineyards, finally the Alps and Rapperswil come into sight. The arrival in Rapperswil is spectacular, you have the best view of the town spread over a hilly peninsula in the lake, with the Alps in the background.
My boat (and probably most of the others) had a restaurant where I enjoyed a glass of local wine and mineral water. Others had a meal and it looked like they were quite happy about the quality.
The boats are part of the ZVV public transportation network. If you have the Zürich Card (I did) then part of the cruise is covered. Buy an additional ticket for the rest of the trip, 5 zones are required if I recall correctly, which adds up to 10.40 CHF for the single trip. Or buy the 24 hours "Anschluss" Ticket, which costs twice as much, but covers the trip back, too, and you can break up the trip anywhere you want. Btw, no matter if you use boat or train - both cost the same as fares and rules of the ZVV apply.
We caught the 13.30 boat from the Buerkliplatz ship station in Zurich.
We purchased our tickets here, from a machine (easy to use - Multi lingual instructions) - The 9-Uhr (9 hour) pass, which on a Sunday is valid for the whole day! This cost CHF 24.00, and covers train and bus/tram travel too - Great value, especially as Sonya and I visited Uetliberg later that day, before returning to Zurich
This service is very popular - get to the quay early if there is a group of you, if you want to sit together outside.
The boat that we travelled on had a dining room and bar. It was one of the more modern boats. There are still two of the old Paddle steamers in use - we spotted one during our journey (pic 3)
During our journey, we enjoyed sandwiches and a drink. A couple sitting near to us enjoyed a couple of glasses of Prosecco.
The boat called at a few places en route, before we arrived in Rapperswil, about one hour and 45 minutes after departing Zurich.
We returned to Zurich by train - quicker, but less scenic!
You can also take this line from Rapperswil ( with signboard to (RAFZ) passing to another route, to the countryside via Uster and Stadelhofen. The ride takes you to Zurich Mainstation in 36 minutes or vice versa.
This train is commuting from Rapperswil every .52 mins after an hour passing through the lakeside and arriving in Zurich Main Railway Station in 40 minutes. This line is going further to Winterthur or the other way round.
Take a cruise and your time to discover the Zürich Lake. We took the MS Linth for a 1h45 trip from Zürich Bürkliplatz to Rapperswil harbor. A lovely and gourmet cruise but with an happy end... not as in Titanic... we all survived but one camera doesn't!
The local cruising company owns also 2 steam paddle boats the DS Stadt Zürich and the DS Stadt Zürich.