It's January 2024 and Akkerman launched a limited Edition ink 'Out of the Blue'. For those who don't know: Akkerman is a fountain pen shop in The Hague, The Netherlands (tnot to be mistaken with the Amsterdam Akkerman: they parted ways decades ago). For some years now they're offering their own line of inks in a very distinctive (and very usable) bottle.
Although there is no official confirmation (at least I don't know), it's generally thought the inks are made by Diamine. In this case I think the ink is just a rebranded version of Diamine Sargasso Sea. The only difference I noticed is that the very distinctive smell of the Diamine ink is less pronounced here. In my opinion that's a good thing: I really don't use Sargasso Sea because of it (even uncapping the pen is enough).
My opinion: lovely blue ink. A real presence, without it being too much in your face. Very well behaved, wet, saturated. As expected the water resistance isn't great, though not nearly as bad as I had expected. Is it a keeper? I don't know yet, just one hour of playing with this ink isn't enough yet.