The Xindi-Aquatic scout ship was a Xindi-Aquatic starship used in the 2150s. It was much faster and more maneuverable then the Aquatics' main cruiser.
The Aquatics sent five vessels of this type among the Xindi fleet to assist the starship Enterprise NX-01 in their fight against the Reptilians and Insectoids to destroy the Xindi weapon before it could attack Earth. One scout ship was disabled by the enemy fleet, another was destroyed by Dolim's warship, and at least two others were crippled by spatial anomalies created by the Sphere-Builders. (ENT: "Azati Prime", "Countdown")
In the final draft script of "Azati Prime", the vessels of this configuration were simply called Xindi-Aquatic "ships".
In Star Trek Online, this class of ship is called a "Mobulai Frigate" and is available as a hangar-based fighter craft exclusive to the Xindi-Aquatic cruiser, dubbed the Narcine Dreadnought Carrier.