The first piece of optional equipment that you could bring with you on the trip is either a dive table or a dive computer. One of these is needed with each group of people that are diving so that you know how to descend and ascend when going scuba diving. Drastic pressure changes are extremely dangerous and can prove to be fatal if done too quickly. Another piece of equipment that you can bring with you on a dive trip is a weight belt or additional weights. A weight belt is used for any dive under twenty or thirty feet so that you can actually go underwater. Your body, because of the amount of oxygen in your lungs, causes you to rise in the water; a small amount of weight added to your waist or shoulders will provide the extra weight needed to push your body deeper into the water.
Some of the other pieces of equipment that you can bring are underwater cameras to capture memories under the water, a knife with a sheath that can be used to dislodge items underwater and protect yourself in extreme circumstances, collection bags with floats and flags enable you to collect things underwater and then release them to the surface for pickup later, and small oxygen kits for emergencies when your main oxygen tank stops working. Any of these items can make your diving experience more safe and enjoyable.