Jelly shoes (or Jellies) are shoes made of PVC rubber. Jelly shoes come in a variety of brands and colours. Jelly Shoes were designed after World War II when there was a leather shortage in Europe. They were very popular in the 1980s till the 1990s when a pair could frequently be purchased for under a dollar. They resembled sandals and were most commonly flat shoes with a little heel. Related are flip flops and sandals.
Many thanks both of you. I couldn't get it on google but as soon as I saw your answer, I remembered them. A bit uncomfortable I think - fortunately I had sandshoes instead.