One of the things I forgot to mention about Mel Odom's Threat From The Sea, is how with a few key phrases and scenes, he gives the sahuagihn some life that makes their purpose and motivations stand out.
For one, the saying meat is meat. It represents how for those who live under the sea that supplies can often be in short supply and that even other sahuagihn can be meat.
The other one is something like We Who Eat. While people call them the sahuagihn and they themselves do at the same time, it also showcases that a culture can have a specific name for their own people.
In addition, the way of life for these creatures, includes a belief that those who fail or die, were too weak to live. A true survival of the fittest. In those cases when it was a strong sahuagihn who died fighting against a ruler in a blood feud or challenge for example, their mantra of meat is meat allows the strength of that fallen one to be passed onto the rest of the tribe.
When adding unusual races and monsters, thinking about how you can make them more then just a gathering of random statistics will go a long way in making memorable encounters.