Plastic socks are available to protect the feet and avoid spreading verruca while swimming. However, the official advice from Swim England says:
“The use of devices, such as plastic socks, to protect the feet should be discouraged. As with elasticated knee bandages, the socks have limited value other than of attracting attention.
“The use of a waterproof plaster is sufficient to cover the verruca during lessons.”
Many people now wear flipflops to go from changing room to poolside. Check your local pool’s policy if you are unsure.