Keep it Closed
Keep the cooler closed, out of the sun, and covered. If possible, bring two coolers: one for drinks and snacks, and another for more perishable food. The drink cooler will be opened and closed a lot, which lets hot air in and causes the ice to melt faster. Pack your coolers with several inches of ice, blocks of ice, or frozen gel-packs. Store food in watertight containers to prevent contact with melting ice water.