What happens when 9,000 tons of steel hit a sandy bottom less than a mile from a coral reef in the nation's preeminent marine sanctuary? There's a high probability of a world-class dive site, which will enhance tourism. But what about all the fish and invertebrates that make the wreck their home? Where do they come from? Does the wreck alter the concentration of native marine life on nearby natural reefs? Are the fish on a wreck congregated and therefore easier to catch? Important questions such as these are central to any discussion of the liabilities and benefits of artificial reefs.