The Cliff at The Sentosa Spa and Resort, formerly the Beaufort resort. overlooking the south chinese sea, excellent dining, but quite pricy.
La Vela at Keppel club will also fulfil your sea view dining expectations, but for whatever reason the place is swarmed by mosquitos and flying ants, which will crawl around and in your food, at least that was my experience. But very good food and nice setting.
Another nice experience is to dine on the water, with the Cheng Ho ship (
www.watertours.com.sg ), which is Asian buffet dinner served, while cruising the marina and around a few islands at 6.45pm every night.
Halia at Botanic gardens won't let you face the sea, but it is fantastic food in a romantic ambience and in the midst of the gardens, squirrels provide you with their musical sounds
Patara Thai restaurant in Raffles City is very good and nice ambience, nice views of downtown.
Indochine at Emperess place, facing boat quay is high quality and can be romantic too, if not too crowded.
Eric