Urban Mermaid: Book One in the Tales from Colony Island series

Ever since grade school, Penelope Tench has known there is no one on Colony Island she is interested in. She wants to find a mate and have a family someday, which seems to leave her with only one option—however, mermaids are strongly advised not fall to in love with humans.
After graduating with a degree in Finance, Penelope begins living a lonely and isolated life in the city and shuts out her family and friends. While spending a Saturday in the ocean, Penelope lies under a dock contemplating her life. When a human male walks out on the pier, instead of staying hidden, she pops above the surface, gives him a scare, and then chats with him before flashing her tail and disappearing underwater.
When she reports for her new job the next morning, she’s introduced to Peter MacPherson. They immediately recognize each other from the dock the previous day. He assures her he’ll keep her secret—then volunteers to make her weekend swims safe, secure, and enjoyable by handling all the logistics: motels, meals, drop-offs, and pickups. Over the next few months, Penelope begins enjoying being a mermaid again and develops feelings for Peter. So, she takes a leap of faith—and gets into bed with a human.