A Thousand ft. Below

Merfolks... Who says they don't exist?
A thousand feet below lives the half-human, half-fish mythical creatures.
A kingdom where humans are not allowed.
For humans are selfish people.

One day, Serena, a normal teenage girl, accidentally steps foot, (or should we say, drowned and was saved by a merfolk) in the magical Kingdom. Will she survive and blend in with the merfolks? Or will she be doomed?