I suppose the underwater scenes were cool and ground breaking when it was made but really the movie is pretty poor.
I think the underwater scenes took an incredible amount of work and are still pretty innovative. Many unique underwater vehicles were created almost from scratch and directing a scene with so many elements was quite a challenge. But yeah, it may be the weakest of the Connery' Bonds. However, for me I'd take any Connery over any other Bond. He was James Bond, if only because he existed in the timeframe of the books. You've got to wear those fedoras.