The Xindi-Aquatic escape pod was a type of small one-man escape pod of fairly typical design used aboard Xindi-Aquatic cruisers. This type of vessel was had no armaments, and was capable of maneuvering under water.
The Aquatics used one of these pods to clandestinely transfer Jonathan Archer back to Enterprise NX-01 after he was captured by the Xindi in the Azati Prime system in early 2154.
Archer later assigned Travis Mayweather and Hoshi Sato to analyze the pod for any useful information they could find. Although the ship itself contained no significant revelations, Sato did discover an encrypted message in its database left there by Degra revealing secret rendezvous coordinates. (ENT: "Damage")
In the final draft script of "Damage", the Xindi-Aquatic escape pod was described as "ultra-sleek" and "strange".