Pre-chill everything and layer ice like a lasagna.

Yes, but the real trick is thinking like a refrigerator, not a bucket.

Most people toss warm drinks on top of ice and wonder why it melts in hours. The science is simple: heat moves to cold. Every warm can you put in is a heat bomb that melts ice faster. So pre-chill everything—drinks, food, even the cooler itself if you can. Stick it in the fridge overnight.

Then layer: a thick base of ice, then food, then more ice on top. Cold air sinks, so the bottom stays cold naturally. The top is where heat gets in every time you open the lid, so that top layer of ice is your shield. Pack it tight—air gaps are your enemy. And drain the water? No. Cold water actually holds cold better than air, but it also soaks your sandwiches. Use a separate bag for things you don’t want swimming.

Get a good cooler, obviously. Rotomolded is worth it if you go camping. But for a day trip, the cheap one works if you pre-chill and pack dense.

Future you will thank past you when you’re still crunching ice on hour twelve.