Preheat your oven to 300°F. That way, the heat stays steady once your pan goes in.
Line a rimmed baking sheet with parchment, or skip it if you want extra caramel edges.
Add water, sugar, and peanuts to a medium saucepan over medium heat.
Stir often as things warm up so the sugar dissolves around the peanuts.
Bring it to a full boil and keep stirring until the liquid is gone.
You’ll see the coating get grainy and stick to each peanut.
Spread the coated peanuts in a single layer on your baking sheet.
Sprinkle sea salt evenly over the top while the coating is still hot.
Bake for 20 minutes for a lighter crunch, or up to 30 for a deeper color.
Give them a stir halfway through so everything browns up nicely.
Take the pan out and let the nuts cool completely on the sheet.
The coating gets crisp as it cools; classic crunch, right there.