Katharine McPhee -- Her Bikini Body Is Smashing!

Soon-to-be divorcée Katharine McPhee did a little advertising on the beach in Cabo this weekend ... showing off her tan-lined body less than two weeks after pulling the plug on her marriage.

As TMZ first reported, McPhee said in her divorce docs she and hubby Nicholas Cokas were separated for seven months before she was spotted locking lips with "Smash" director Michael Morris.