You're pretty much stuck eating at your resort restaurants, which may have limited choices and are expensive. Even if you want to try the restaurant of the next resort, it can be a long distance to walk there.
However, if you have your own wheels or join one of the hotel-arranged "excursions", the fishing village of Sungai Rengit, some 30 km away, has a few seafood restaurants. Oddly, the much closer Tanjung Balau does not have any. There are also a few basic restaurants in Bandar Penawar.