Diamine Sargasso Sea is a royal blue fountain pen ink, with a bit of a purple undertone and copper sheen. It's a standout in Diamine's regular line of inks, not only because it's one of their rare sheening inks, but because it's genuinely beautiful, rivaling a few of my favorite Octopus sheening inks.
This is a dye-based (non-permanent, non-waterproof) ink.
