Transtejo Soflusa runs the Tagus crossings as scheduled public transport, and its published 2026 tariff is the honest yardstick for anyone whose real goal is to see Lisbon from the water.
Its own fare sheet prices a single Cacilhas–Cais do Sodré crossing at €1.60 as a paper ticket and €1.55 as a zapping validation on a navegante card, the card itself €0.50. Belém–Porto Brandão/Trafaria is €1.50, Seixal €2.85, Barreiro from Terreiro do Paço €2.95, Montijo €3.25. Cacilhas takes under ten minutes, three or four boats an hour, from before six in the morning until after one at night.
Two people cross to Cacilhas and come back for €6.40, against two seats on the cheapest cruise here at $21 each. The crossing is worth making: the cacilheiro puts the whole Baixa and Alfama frontage behind you, and on the far side the Elevador Panorâmico da Boca do Vento lifts you up the cliff for nothing, with the Jardim do Rio below it and the seafood restaurants along Cândido dos Reis minutes from the pontoon. The Cristo Rei sanctuary above Almada is free to enter; only the lift up the 82-metre pedestal is charged.
What €6.40 does not buy is the run downstream. The Cacilhas ferry crosses; it does not sail the monument reach past Alcântara, under the 25 de Abril bridge and on to the Torre de Belém, the stretch every boat on this page exists to show you. It has no commentary, no drink and no deck to sit out on for ninety minutes, and it lands you at a bus interchange rather than at sunset in open water. Belém–Porto Brandão is the better sightseeing bargain of the two at €1.50, but it is still a working crossing, not an evening.
There is one combined ticket worth knowing about because almost nobody prints it: Transtejo's 2026 sheet lists a 24-hour Carris/Metro de Lisboa/TTSL ticket at €10.35 that covers the trams and metro and the Cacilhas ferry. That is the whole DIY version of this page — tram 15E to Belém, metro to Oriente, the crossing and back — for less than half the cheapest cruise. From three journeys a day it pays; below that, load zapping, because a tram single is €3.30 from the driver and €1.72 off the card.