I'd say you are both on the right track, I found this
https://www.io-warnemuende.de/Antworten_Fragen_zum_Meer.html?frage=41

Sorry that it's only in German, Jadran, I couldn't find an English version and I can hardly translate it myself - too scientifc!

PS: Nice catch Florian. I like the colour of the water. Makes me want to go swimming:-)

Hello Florian, once again :-)... the Italian river Po (flowing into the Adriatic sea just a bit North from Ancona) is an occasional great-great *polluter* ,, and then, moreover, the sea current on the Adriatic sea flows in the direction from the very North to the South along the Italian coast !!!
I do hope my explanation is in good order; cheers my friend Flo!
Jadran

Well, at least it's not just photoshop... 😊😊😊
Jadran, your explanation sounds logical, but do you have an idea, why the colour of the sea in Ancona is so different from time to time? Just a few examples:
http://www.shipspotting.com/gallery/photo.php?lid=2594439
http://www.shipspotting.com/gallery/photo.php?lid=2547383
http://www.shipspotting.com/gallery/photo.php?lid=2583680
http://www.shipspotting.com/gallery/photo.php?lid=2514466

Florian,, I think the main reason for the different colour of the sea is: :-)
- the Italian coast of the Adriatic sea is *muddy* sea bottom;
- the Croatian coast of the Adriatic sea is *rocky* sea bottom;
I hope I am correct, however, can somebody, any expert on the sea *flora & fauna* confirm!
Remaining with very best regards /Jadran

Well... I' d say, I prefer your blue colored sea in Croatia, Jadran! ;-) But to be honest, on this special day, the colour of the italian sea was truly remarkable indeed. Almost toxic... Maybe because a stiff breeze of gale force 5-6 was blowing during the whole day...

Obviously, In Ancona the colour of the water seems to change quite frequently. On this photo, for example, the water is beautifully blue, almost like in the Aegean – or in Croatia of course... ;-) http://www.shipspotting.com/gallery/photo.php?lid=2539910

Probably it depends quite a lot on daytime, weather, perspective and so on. But I'm far away from being an expert in this.

Thank You for your interesting observation and also for the personal memories! Always very interesting! The linked ferry looks especially nice. So I hope, you really enjoyed your time on board and at the port...!

Many thanks for your kind comment again and best regards to Rijeka,
Florian

Interesting,, how the sea at the West coast of the Adriatic sea ( Italian coast) is so *green* whilst the sea at the East coast of the Adriatic sea (Croatian coast) is of remarkable *blue* colour;


Florian,, I also like Ancona very much,, have some unforgettable memories from Ancona since 1966...... (actually, the subject was the inauguration voyage of the newly built ferry "Jacopo Tintoretto" on which I attended as a guest having only 16 years then, http://www.shipspotting.com/gallery/photo.php?lid=713276 );
Kind regards,
Jadran