I need a fire-making kit that will withstand deep immersion in saltwater. It's for my scuba survival belt. No, of course I can't use it while I'm on the water, but it would be useful if I manage to swim to shore or an island. Carbon steel will rust, and stainless steel doesn't make sparks (I'm told). Rubbing two sticks together takes too long, and requires skill I don't have. What two things can I use to strike against each other to produce sparks hot enough to make a fire?
Would quartz crystal & iron pyrite (fool's gold) work, or does iron pyrite rust?