It is not necessary to wear a swim cap when swimming in an Olympic-sized pool, but it is often recommended. Swim caps can help to reduce drag while swimming, which can make you swim faster and improve your performance. They also keep hair out of your face and goggles, which can improve your visibility and help you to breathe more easily.

Additionally, some swimming pools may require swimmers to wear a swim cap to keep hair and other debris from clogging the pool’s filters. This requirement is more common in public swimming pools than in private facilities. If you are going to swim in an Olympic-sized pool, you should check with the facility to see if they have any specific rules or recommendations regarding swim caps.

Additionally,

some people wear swim caps for hygienic reasons as well, to prevent hair from shedding and clogging the pool’s filter and also to prevent the spread of bacteria or lice.

Another reason to wear a swim cap when swimming in an Olympic-sized pool is to protect your hair from the chemicals in the pool water. Chlorine and other chemicals used to sanitize the water can cause damage to hair, leading to dryness, discoloration, and breakage. A swim cap can help to protect your hair from these chemicals, which can help to keep it looking healthy and shiny.

Also, for competitive swimmers, swim caps are often used to identify the team/club/school they are representing. It helps the officials and the audience to identify the swimmers and their teams.

Finally, in some pools, swim caps are required for safety reason. To keep the swimmers’ hair from getting tangled in the pool’s drainage system.

In summary, while it is not strictly necessary to wear a swim cap when swimming in an Olympic-sized pool. It is often recommended for various reasons such as performance. Hygiene, protection of hair, and identification. It’s always best to check with the pool facility regarding their specific rules and regulations.