What would happen to a coral reef if sea levels suddenly rose?

It would be destroyed; coral is a sensitive organism that takes just the right amount of light and warmth to thrive. If the sea levels rise, the shallow-water fish that fertilize the soil and eat the pests would be forced higher than the coral. Deeper water means less light, and in turn, less heat. A drastic water level rise would take away every parameter that coral needs to live, so it would just die, leaving only the already shed skeleton behind.