A large marine Xindi species who communicate in sonar-like song, deliberate slowly and command the biggest ships in the Xindi fleet.
The Xindi-Aquatics are one of the five surviving Xindi species in the third season of Enterprise. They are whale-like water dwellers who take part in Council sessions from a tank and speak in a pattern of calls and clicks that the others find laborious. They are known for taking a very long time to make up their minds and for wanting visual proof.
Their vote is decisive. Archer and Degra show them evidence that the Sphere-Builders, revered by the Xindi as the Guardians, are reshaping the Expanse for their own use. The Aquatics eventually join the Primates and Arboreals, on condition that Enterprise disables the spheres.
Aquatic cruisers are huge and fast. In Zero Hour one of them carries Enterprise in its hold to reach Earth in time to stop the weapon, and afterwards delivers the ship to Earth orbit.