Mermaid 20

Cordelia swam slowly around the wide delta, following the edge. Careful to avoid humans, she often had to stay a long way from the beach. The shallow water threatened to beach her. At times, it was hard to tell where the shore was at all, but she managed. Sometimes she surfaced briefly, but always she kept the beach on her left.
The farther she went, the more the water changed. It tingled on her scales, in her gills. It wasn't painful, but it wasn't comfortable either. It felt weird and she flicked her tail harder, trying to shake off something, but she would shake off her skin or the water. The tingling was a part of her. Even so, she wasn't getting used to it, and then it got worse.
Cordelia had followed trade winds and ocean streams that swept her away. She'd felt an undertow pull her tail from under her. All of these were easily avoided and escaped by slipping out of the way. She'd never had to fight one like this pushing her back to the ocean. If she wanted to follow the narrowing banks, she had to swim against that current.