The Kardashian-Jenner family's Summer vacation in St. Barts [1] isn't all about relaxation and snapping sexy bikini Instagrams [2]. On Tuesday, Kim, Kourtney, and Khloé hit the beach with a personal trainer for a workout in the sun. In true Kardashian style, cameras for their E! reality show were rolling as Kim displayed her pregnancy physique [3] in an all-black fitness ensemble. During a chat with her mom, Kris Jenner, the reality star lifted up her shirt and revealed her growing baby bump. At another point, Kim's sisters appeared to put their muscles to the test in the water. The ladies later reunited with the youngest members of their family, with Kim sharing adorable pictures of North West and Penelope Disick's mermaid costumes [4].