Blood in the Water. The Frontiers, #4

Five years ago, a group of human researchers and their mercenary friends helped evacuate 26 cetaceans from Earth just ahead of their arrest. The world government didn't approve of their giving the cetaceans pinplants, and it wanted to euthanize the dolphins and orcas in their care. After finding a home on the distant ice-covered ocean world of Hoarfrost, the humans and cetaceans settled in. Less than a year later, they were attacked when the planet's previous owners, the aquatic Selroth, tried to regain possession of it.
During the battle, Terry Clark was responsible for inadvertently uplifting the cetaceans, who then came to the aid of the Humans and helped defeat the Selroth. The BotSha and KilSha, as they are now known, have lived a quiet life on Hoarfrost for the last four years, learning what it means to be an intelligent species, while Terry has learned the life of a mercenary. But when they're forced to give up Hoarfrost, Terry and his mercenary company will have to determine where they're going to go and how they're going to get the massive cetaceans to their new home.
Unfortunately for them, they aren't being forced to leave the planet so much as they're being targeted for elimination. Ancient, infinitely wise, and powerful forces have discovered them, and they are out for blood.