Hurricane Katrina destroyed about 18,000 slot machines at floating casinos in the Gulfport and Biloxi areas.Some were washed into the sea. Looters ran off with others. And the vast majority -- about 75 percent -- were destroyed.International Game Technology, the world's largest maker of slot machines, and other big slot makers are picking through the twisted casino barges, trying to salvage machines and reclaim the ones they leased to the gambling companies.They have not found much to save at the 13 casinos that dotted the Mississippi coast.Officials said salt water destroyed the slot machines' electronic insides and caused them to rust.State gambling regulators are supposed to keep track of every slot machine, but Katrina has made that task unrealistic. It is unclear how many were swallowed up by the sea.The recovered machines, which can cost up to $12,000 each, were being shipped to IGT headquarters in Reno, Nev., to be scrapped, or to the Gulfport office to be repaired if possible.