Cannon 100mm macro with IS if you have the money, about a grand. If you want just the canon 100mm macro you can get one used for about 400 and it will do a amazing job. I do not saggest getting the IS if you only are going to shoot coral. Unless you just have money to throw around. I would take the extra money you would save and buy a remote (about 10 bucks on ebay) and a quality tri-pod. Tripods run any where from 50 bucks up into the thousands. Buy a nice one prefferably with a removable head and that has the fetures you want. 7d+remote+tri-pod='s some sick pictures with a little time.
i'm using the efs 60mm f/2.8 usm macro. chose it because i have several buddies who will let you use their 100mm when needed, but so far i love the 60mm!
I shoot Nikon, but agree with the comments on IS. Image stabilization is overrated for macro photography, and not really worth the extra expense. You will be taking most (if not all) your macro photos on a tripod anyway, and even if you don't have a remote, use the self timer, so you shouldn't miss the IS.