These are essentially the law enforcement and military for the Celestial Cetaceans.
They are comprised of mostly Celestial Cetaceans evolved from Brygmophyseter shigensis, but also have some members from most other species that exist.
A significant number of the GW and RF transmissions received by NEMO seem to be from The Brygmophyseter Corps.
Sizes range, but members of the Brygmophyseter-derived species are typically ~23ft long.