Was in college, and visiting my then gf at in her home town.
My g had a friend, let's call her Kate. Kate was sorta alt but not really, and for some reason was not aware of how hot she was, and how big her boobs really were. Like she hated bras or something, or just didn't care...not too sure
We were riding bikes along a boardwalk or sorts at the harbor, which was a popular hangout spot for the younger folk. We were also in bathing suites because beach and swimming.
So I was riding he bike inbetween my gf and Kate, and Kate said something odd, so I looked over to make a wise crack response...she went to scratch he neck and accidentally undid her halter top and it fell all the way down...I got distracted and crashed into a trash can...My gf started laughing, and Kate said "I really hope I'm the cause of that".
They both proceeded with Men can't focus if boobs are around jokes for the rest of the bike ride, and me being all sullen and too embarrassed to even look at Kate.
So my first accidental nudity experience was with two hot women making fun of me for being a typical guy lol