This is just my opinion, but that's Brad and DeAnna (wearing the hot pink suit) coming out of the water after swimming in the ocean. Before that, they rode dune buggys.
After their day of riding dune buggys, they clean up and get dressed for dinner in the evening changing their wet swimsuits to dry clothes (and a new swimsuit that's dry LOL) After dinner, you see them having fun in the pool and that's where DeAnna is wearing the brown top.
This happens with Bettina also. Brad and Bettina go sailing and eventually land in the ocean.

After their day at the beach and sailing, they change into dry clothes and get ready for dinner (She changes into the pink bikini because the other ones wet) After dinner, they get into the hot tub where you see her wearing a pink bikini.
JMO
