Ahh i think i have lace coral. It looks the same but i think its different. @drschell might know more about this.Maybe you have to cut yourself on it...
"Divers often mistake fire coral for seaweed, and accidental contact is common. Upon contact, an intense pain can be felt that can last from two days to two weeks. The very small nematocysts on fire corals contain tentacles that protrude from numerous surface pores (similar to jellyfish stings). In addition, fire corals have a sharp, calcified external skeleton that can scrape the skin." http://en.wikipedia.org/wiki/Fire_coral