Alright, so you want to find the mermaid? Firstly, go to bannan island, secondly, speak to the old wayfarer, listen to his speech closely.
"The mermaid is a sly and elusive creature, she will not appear when monsters lurk nearby." And you must also know that the mermaid is already in Bannan Island.
If you want to know about ferocious winds that blow off the mermaid's clothes, then you should really play Hentai games.