Guess Who This Sweet Summer Kid Turned Into!

Before this New York City native in her little fishy bathing suit turned into a famous singer, she was just running around the Big Apple and breaking into the music industry with her cover of Drake's "Headlines" track.

Her initial claim to fame came from her days on Tumblr, but at just 19 years old ... Atlantic Records signed her. You may have heard her song "Collide" featuring Tyga, and when she's not in the studio, you can find her on social media ... posting hot shots from the gym!

Need one more clue? Just ask her bestie, Hailey Bieber!