Pasta Fresca Da Salvatore at the East Coast Sea Sports Centre used to put tables down on the beach, sand and all. I suppose I'd classify it as romantic as my ex and I used to go there every now and then - it was a great place to dine at 10pm+ and you could see the planes emerging out of the night sky on their approach to Changi which worked for both us frequent flyers.

This was a few years ago though, I don't know whether its still open.