The Praedatori is an organization made up of merfolk who devote their lives to protect the waters from the terragoggs and other mer.
Merrow herself created the organization by appointing the duca. The Praedatori steal from people who are hurting the ocean. They also apprehend the mermaids who are selling out the shoals of fish or sharks to humans. The Praedatori have an above-water branch as well, where they are called the Wave Warriors.
As the Wave Warriors, they stop the terragoggs, or humans, from hurting the animals. Their main focus is on Rafe Mfeme, who is the worst human of all.
The Praedatori spread out all over the oceans, but (until the death riders destroyed it) their headquarters was in the Lagoon, near the human city of Venice.