Be Ready to have fun, but also be ready if something unplanned does happen...
Remember to check Weather and Water Levels when planning your trip, also.
Items to bring:
Water shoes/Old gym shoes
Hat & Sunglasses
Change of clothes- including socks & shoes - leave in your car until after the trip
First Aid Kit (hopefully no need!)
A cooler with ice & plenty of drinks
Fishing equipment (optional)
A ziplock bag or waterproof bag/box (better) for your Important electronic items like your cell phone, radio, etc.
Wear your bathing suit if you want to swim
Boat horn or whistle
Throw rope (to save someone if needed, optional)
Any other important items like lighter/matches, pocket knife, bottle opener, etc...