Bieber, 21, wore a life-vest over his shirtless body. Baldwin, meanwhile, sported a white bikini and a brown sleeveless top. She was seen clinging tightly to the "Baby" hitmaker as they sailed through the waves on the jet ski, reported Ace Showbiz.
Earlier that day, the duo were also seen hanging out together with some friends by the pool.
Bieber took to Instagram to share two photos of him cosying up with Baldwin.
In the photos, the 18-year-old model could be seen resting her arm on the "Beauty and a Beat" hitmaker. He captioned one of the shots, "The one and only @haileybaldwin.