Seurasaari and Korkeasaari
Seurasaari
You walk there. A wooden bridge crosses from Meilahti and that is the whole journey — no ferry, no ticket, no timetable, and it works in any season. The island holds an open-air museum of historic wooden buildings brought here from around Finland: farmhouses, a church, storehouses, set out among the trees on paths. The museum buildings themselves charge in season; the island and its paths do not.
The other thing Seurasaari is known for is the wildlife, which has entirely lost its fear of people. The squirrels will come to you and the ducks will follow you. Children find this considerably more memorable than the architecture, and that is fine. More no-ticket afternoons like it are on the free things page.
Korkeasaari
The zoo, on its own island, reachable by bridge and bus all year and by JT-Line boat in summer. The boat is the pleasant way to arrive if the season allows it, leaving from the same Market Square quay as the other island services, but it is an option rather than a requirement. Going by bus works in January.
Why this confuses people
Because Helsinki genuinely is a city where you get to places by boat, so visitors reasonably assume every island needs one. Some do: Suomenlinna needs the HSL ferry, 15 minutes from Market Square on a city ticket. Vallisaari and Lonna need JT-Line boats and only run in summer. Pihlajasaari boats leave from Merisatama and Ruoholahti. Harakka has a summer ferry from Kaivopuisto. Isosaari is about 40 minutes out. But these two do not, and knowing which is which saves a day. The island hopping page has the full list with the piers.
And the sightseeing boats
A loop from Market Square does not stop at either of these islands, or at any island: it goes out through the channels, shows you the city front and the fortress from the water, and returns to the same quay in about 90 minutes. It is for looking, not for arriving. The decision page makes that split properly, and it is the distinction I explained most often from the kiosk.
Seurasaari works on a wet day and works in winter, because the bridge does not have a timetable. Keep it in reserve for the afternoon when the water plans fall through.
Frequently asked questions
Do I need a boat to get to Seurasaari?
No. You walk over a wooden bridge from Meilahti, in any season.
How do I get to Korkeasaari zoo?
By bridge and bus all year, and by JT-Line boat from Market Square in summer.
Do the sightseeing boats stop at these islands?
No. The sightseeing loops do not land anywhere — they return to the same quay at Market Square.