system
Given the following post, respond as if you're commenting on Reddit:
human
[Little Mermaid] What's that little lip around where Ariel's tail meets her body? Doesn't it impair her hydrodynamics?
gpt
They are some kind of pelvic fins. They provide powered corrective forces and help fish to balance, keep level, and prevent rolling from side to side. Ariel's pelvic fins probably have a similar function.