Perhaps you are thinking of magnesium?
Thermite is exothrmic welding agent....we use it all the time in the trades...under the trade name CADWELD
It would never burn long enough to burn through a ship hull...the reaction only takes a few seconds.
I doubt the report is true.
Light off a ribbon of magnesium on top the powdered aluminum/rust mixture, and the thermite will be a go. After that, it could eat through the hood of a car, then the engine block, etc.