There are two regular boat connections between Vienna and Bratislava.  Boat services operate only from April till October:

Twin City Liner:                            

http://www.twincityliner.com/

TA Review:  Twin City Liner 

Twin City Liner on the way to Vienna 

Twin City Liner is a modern jet-propelled catamaran, operating between Bratislava (pier next to hotel Devin / Rigeleho St.) and Schwedenplatz in the center of Vienna. There are up to 5 daily connections during the main season. Travel time: 1h15m to Bratislava, 1h30m to Vienna. The service operates from April till October.

 

L.O.D Hydrofoil service:               

http://www.lod.sk/en/international-cr...

TA Review: Vienna to Bratislava Hydrofoil 

This service uses Meteor, Russia-built hydrofoil (winged ship), operating between Passenger Port (Fajnorovo nabrezie - next to the building of Slovak National Museum) in Bratislava and Schiffstation Reichsbrücke, Handelskai 265 in Vienna (close to Prater). There is 1 daily connection during the main season. Travel time: 1h35m to Bratislava, 1h45m to Vienna. The service operates from May till October.

 

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