It was not that the mermaid was beautiful, but that she was mesmerizing a group of sailors on a ship, causing them to veer their ship towards them. But instead of jagged rocks and a dangerous island, like Lex had heard in stories back on earth, the mermaids were attracting them towards a sales booth.
They were selling deep sea items, though the usefulness of those items was questionable. After years of practicing with his Glyph that could identify treasures, Lex had developed an innate understanding for the value of random objects, and he could tell that nothing they sold was particularly precious.
Lex used a simple illusion technique to alter the appearance of his face before teleporting down to the booth.
"Excuse me ladies," Lex said warmly, "could you possibly point me towards the continent? I'm a little lost."
The mermaids looked at him, then looked down at their booth. The meaning was simple. Buy something before asking them any questions.