Sirena grew up in the Mako Island pod, and has been Nixie's best friend since they were hatchlings. She is very close to her sister Aquata and is very upset when she and the pod left her, Lyla and Nixie by themselves on Mako to sort things out,Sirena is a little naïve, very trusting, can be unsure of herself at times and is easily treated like a doormat. Where Nixie is the leader, Sirena is the follower. She is loyal almost to a fault. She is a little clumsy and of all three mermaids, struggles with legs the most.
Although the others rarely pay attention to what Sirena has to say, she has sometimes come out of left field with a streak of genius that can help them find their way out of sticky situations. As the series progresses, placid Sirena gradually earns the other mermaids' respect as an important member of the group.