Barbie Blue Nautical Halter Dress Identification?

Question:
Blue Nautical Barbie Halter Dress - It has a genuine barbie tag inside. snaps in front and ribbon wraps to tie in back.

My Answer:
I thought this one was going to be easy - I have that dress, it was in a collection I acquired and a Malibu Barbie was wearing it. (I also had a long dress I wore to a dance in 1976 that was very similar!) But I can't find it anywhere - which may mean it was 1980 or later. I do not think it came on a doll. Anyone know this dress?