Swimming Without A Net: Number 2 in series - Fred the Mermaid Trilogy

Half human and half reluctant mermaid, Frederika Bimm finds herself investigating her watery roots. After spending her entire life without seeing another mermaid or merman, there are suddenly undersea folk all over the place when Fred visits Black Sea. But Fred is still torn between her attraction to Artur, prince of mer-people, and human Thomas.