Chrissy Teigen Is Now Serving

No, Chrissy Teigen is not on vacation in Hawaii, but she's definitely hanging loose with John Legend ... and 3-month-old baby Luna.

The ridiculously gorgeous fam is chilling on a yacht off St. Tropez ... like a ton of other celebs this week. We're guessing Luna and John are big fans of mama Teigen's outfit.

Mom boobs -- they're not just for kids.