REST API

From the dataset abstract

Helsinki Region Transport's (HSL) LATI Web service is a ferry traffic statistics application commissioned by HSL. The system records the number of passengers, transported vehicles and passengers and/or vehicles that did not fit on the departure in question.

The ferries MS Suomenlinna II, MS Suokki and MS Tor operate from Kauppatori to Suomenlinna. The maximum transport capacity of MS Suokki and MS Tor is 350 persons and MS Suomenlinna II 395 persons.

The service ferry MS Ehrensvärd operates from Katajanokka to Suomenlinna. MS Ehrensvärd can also transport trucks and lorries and can take a maximum of 200 passengers.

More detailed description of the API: https://hsl.louhin.com/lati/help

Source: Suomenlinnan lautan matkustajamäärät