Here is a list of items to bring on every club sea kayak trip, including day trips and overnight trips:
Wool, pile or polypro sweater/shirt and pants to wear under a wet suit. While sea kayaking, it is important to be able to adjust your insulation to suit the conditions, so multiple layers are important. Be prepared for a range of conditions from cold and windy to hot and calm. It should be possible for you to add or remove layers while on the water.
Old sneakers you don't mind getting wet (or neoprene booties, if you have them). Wear wool socks inside these, not cotton! Tuck shoelace loops and ends under the crossed-over parts of the laces between the eyelets, since loose loops could get caught on your footpedals and trap you inside the boat during a capsize!
Sunscreen, sunglasses, and a hat to protect you from that bright orb in the sky.
A few dollars for gas. Exactly how much depends upon the distance of the drive, the number of riders contributing, etc. If you have doubts, ask the driver what seems fair. (Remember, dragging boats around also makes for a significant amount of wear and tear on a vehicle, which can be more costly than petrol.)
Food and water. (Bad things happen to dehydrated, hypothermic (or hyperthermic) boaters.) For overnight trips, contact the trip coordinator about possible shared food arrangements.
Chocolate for the trip coordinator(s). (Extremely Important!!!)
For overnight trips, the gear requirements multiply. The club does not own camping gear; all camping gear for overnight trips must be provided by trip participants. If you'd like some advice for what to bring on an overnight club sea kayak trip, club trip coordinator Mike Wagenbach has written this informative essay entitled, "Fundamentals of Kayak Camping Gear."