If you are going to be kayaking on spring and summer afternoons where the weather is mild to hot outside, you will not want to wear a wetsuit.
Looking at the flipside, however, if the water is freezing and it is a bit chilly outdoors, then you may want to invest in some wetsuit as part of your kayak accessories.
These types of items are designed to trap your core body heat to provide you with warmth. You can even go with hoods, gloves, and boots to provide your body with full insulation.