The 43-year-old Hungarian sailor was killed during a landing manoeuvre of the passenger ship MS Belvedere. His crew mates witnessed the incident, and immediately began a rescue.
Despite resuscitation attempts, the man died at the scene, according to police spokesman Thomas Keiblinger.
The accident occurred around 2am, while nearing another ship that was anchored at the pier. A colleague noticed the man falling into the water, and immediately raised the alarm.
Sailors launched a dinghy into the water, and caught up with the man after he had floated 20 metres from the ship.