Do I have to wear a wetsuit?
It is recommended to wear a wetsuit, but not mandatory. Most swimmers do wear one.
The water temperature is usually warm enough to not need a wetsuit but the water temperature in the middle of the lake can be a little cooler, so a wetsuit will keep you warmer and you'll also benefit from the added buoyancy. Some swimmers do not like the restriction of a wetsuit, but it is personal preference.