Few pairings talk this easily this fast. Sagittarius and Aquarius sit sixty degrees apart, and the sextile is exactly that: low-effort chemistry, the kind where a first conversation runs three hours and neither notices the time. Fire and Air feed each other cleanly - the archer's enthusiasm gives the water-bearer's ideas somewhere to burn, and Aquarius hands Sagittarius a cooler, stranger angle on the beliefs it holds too warmly. There's stimulation without much friction, which is rare and worth naming.
What binds Sagittarius and Aquarius
What actually binds them is a shared allergy to being fenced in. Both prize independence over reassurance, both would rather have an interesting argument than a comfortable silence, and neither mistakes distance for rejection - you can leave an Aquarius alone for a week and a Sagittarius on the other side of the planet, and the bond doesn't dent. They give each other room as a form of respect. The upside is a relationship with almost no clinginess; the downside is that two people this good at space can drift into being excellent acquaintances who forgot to build anything deep.
Fixed anchor, mutable weathervane
The modes are where the texture lives. Fixed Aquarius holds a position - often a principled, immovable one - while Mutable Sagittarius flexes and reconsiders and moves on. Usually this complements: the water-bearer anchors, the archer keeps things from ossifying into dogma. But when Aquarius digs into a conviction and Sagittarius keeps poking at it for sport, the anchor-versus-weathervane dynamic can turn into one person feeling lectured and the other feeling flighty. It helps when both remember they're on the same side of most fences.
Beyond the sun signs
As friends, this is one of the genuinely great combinations - big ideas, shared causes, adventures planned over coffee and occasionally even taken. As lovers it can be thrilling and unusually free, though it sometimes needs deliberate tenderness to keep from cooling into friendship-with-logistics. Keep the sun-sign read in proportion, too: two Suns getting along is roughly one part in thirteen of the actual synastry. Whether the warmth holds turns on the two Moons, the Venus signatures, and how each Mars wants to be met.