Studio at Montage is fantastic. As it is on a cliff in its own building, I would say they have the most dramtic view. It is a great place for worthy dates, and important business meetings. Food is excellent, however come with a very steep price.
Alternatively, you can try the other restaurant at Montage. I haven't tried their food, but my colleagues told me it is very good. The view is more set back, nevertheless it is a great view.
Another my favorite place is Ti Amo (italian). If you go to second floor, you will have a great sunset view. However, I can't remember how great a water view is, as somehow I never paid attention to that. You might want to give them a call and find out. Ti Amo is on the water side of the PCH.
If you don't have to be right on the water, and ok with a very short walk, I will suggest you consider Sun Dry Tomato (California). That is my favorite lunch date place with my wife. Several patio seats have distance water due to the seating angle. It is right on Forest street in downtown laguna. you should call ahead for reservation, and bring a light sweater.
231 Forest across the street has excellent food, but no water view. but you can always have a nice dinner and walk down the street for a cup of starbucks before hitting the beach.
also, you can consider having a drink and an apetizer at the bar in Montange or studio for the great water view, then go somewhere else like sun day tomato / 231 for dinner. This way, you hit two places in one night.
Good luck and have fun!