These ships were used the Xindi Insectoids during the mid 22nd century. They were assault vessels, quite heavily armed for their size with half a dozen particle cannon. As is usual for Xindi Insectoid ships they have a spiked design, in this case with a single extendable spike on the ventral surface. The ship had a much more powerful structural integrity field than would be expected for this period, which allowed it to operate under water.
The NX-01 recovered one of these craft from a crashed Xindi ship in 2154. The ship was used by Commander Reed and Ensign Mayweather to locate the final version Xindi weapon design to gather intelligence, and then again in an attempt to destroy the device. Unfortunately the attempt failed and the craft was captured by the Xindi.