Zombie Love has Bothered Me for 30 Years

I've been wondering about a horror movie for 30 years, probably a 1970s film.

The synopsis:
A horror/love story where a couple vow never to part - the man then dies in a freak accident but returns because of the bond they made. He starts rotting and becomes zombie-like which drives her near insane. They end their life together on a causeway and drown. The film is set in a fishing village/town.

Sorry, I was quite young when I watched the film and this is all I can remember, but it left quite an impression on me.

I need to know soon because my husband is beginning to smell a bit... no really... I mean it.

Help Please!