One of the boat seat accessories that one must have is a seat cover. When your boat is anchored on the dock or parked in some other facility, make sure that all your seats are covered.
Covering seats keeps the seat protected against harsh sun, dusk, and insects. It increases their longevity. Another accessory that you can use to enhance the look of the boat is under-seat lighting.
This will illuminate your boat and give it a fun look. These lights are easily accessible in online stores. They are inexpensive but impactful.