Nitro Powder

Nitro Powder (or TNT in the original) is an item that Nerrick the dwarf uses to blow a whole that allows your ship to access to the rest of the world's waters. It is obtain in a chest in Corneria Castle. In order to get it, you must obtain the Key first by the Elf Prince in Elfheim and head by to Cornelia and find it in one of the locked doors.