For a recent camping trip I had to get a large cooler at short notice. As large coolers are expensive and I didn't know if I'd ever need it again, I decided to upcycle an old fishmongers box.
To obtain the box I went round my local supermarket fish counters until one kindly gave me a box, in this case from a recent delivery of Salmon.
Step 1: Step 1 - a Thorough Clean
Once you have your soon-to-be cooler, give it thorough clean to remove most of the fishy smell and any bacteria that may be lurking...