Impossible? Take a look here.
The catch is - it's not a ship! It's an offshore heavy lift jack-up vessel and it's mounted on those vertical rails which go down all the way to the bottom of the sea where they are firmly embedded into the seabed:
Those rails can then be retracted and the whole platform becomes floatable and can be moved or towed away to another position.
Rails retracted and sailing away, on its own propulsion
Very similar platform in its fully operational state: jacked-up, embedded and with crane deployed
This very vessel/platform was built in the nearby shipyard (Uljanik, Pula, Croatia) and was launched into the sea in August 2017.
Of course, before actual delivery, the platform has to be thoroughly tested which involves lifting the vessel up to the maximum height, to test for stability and maneuverability. And that's exactly what happened here - the vessel was tested and lifted 90 meters above the sea-level, where it was visible from far away.
More pictures:
Last five pictures were taken from this article, a local web-portal wrote a little story about the whole occasion (in Croatian):
http://www.regionalexpress.hr/site/more/kud-plovi-ovaj-brod1