A volunteer at a beach clean in west Norfolk found a 25-year-old crisp packet.
Erna Gotyar, who organised the beach clean in Heacham on Saturday, said the volunteer had found the crisp packet after it washed up from the sea.
'When the volunteer gave it to me it was still a bit wet,' she said. 'It was still in good condition.'
On closer inspection, Miss Gotyar found details for a competition on the packet - with the closing date for entrees on December 31, 1993.
The cheese and onion Walkers crisp packet was one of many items found on the beach clean, which was held as part of the Marine Conservation Society's Great British Beach Clean.
Items included 80 cigarette butts, 53 plastic pieces and seven dog poo bags.
Earlier this year, a woman found a crisp packet dating back to 1967 on Caister beach.
Miss Gotyar said: 'It is really shocking. This is why I want to raise awareness, we have single-use plastic like this crisp packet and it blows away God knows where.'
Miss Gotyar is also single-handedly launching the Refill project in King's Lynn in a bid to tackle single use plastic.
She is encouraging businesses in the town centre to join the campaign which allows the public to refill their water bottles for free.
'After my first beach clean I started attending more beach cleans and picking litter up whenever I can, I started learning about the scale of the problem and my desire to act grown stronger.
'I realised I am adding to this problem so I started getting rid of single plastic from my own life - it is really difficult to detox from single-use plastics but even just taking one step at a time makes such a difference. For example carrying your own water bottle, taking your own shopping bag, saying no to straws and taking your own lunch with you.
'I am making conscious decisions to reduce my plastic footprint whenever possible by choosing non-plastic materials built to last, and I would like to encourage more people on the way.'
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