It was a distinctly underwater-adapted tongue. It combined elements of aquatic elvish, the merfolk language, and the shalarin base language, and also contained dolphins' clicks and whistles. It also included constructions from the locathah, the kuo-toan, and sahuagin languages.
Members of all these races could speak and understand Serusan, but only comprehend the most basic subjects. One still needed to learn fluency in it to communicate fully.