Wetsuits provide buoyancy. This can come in handy for any open water swim “panic” as the wetsuit will give you extra lift and make it easier to float while you bring your heart rate down and your focus back to swimming.
The buoyancy of the suit allows the wearer to swim faster than without the suit. A swimmer can expect to save anywhere from a few seconds to tens of seconds per 100. Usually, the longer the distance the more the savings are noticeable.
The wetsuit can provide warmth to the swimmer in the cold water. If you are sensitive to the cold this can be great at making you more comfortable in the water.