"Provocative pictures of teenagers in swimsuits" is child pornography. It's the "provocative" part that's important. Even if there isn't any nudity, if the focal point is on the child's genitals and framed to elicit a sexual response in the viewer, it's considered pornographic.

These weren't candid shots of the beach. These were posed children. The reason I'm not describing them well is because it's making me uncomfortable to continuously describe them to people who are coming into this discussion with no idea what was posted. You have no idea how queasy I feel typing "child's genitals".