BACKPACK - For carrying food, equipment, etc. A dry bag inside to keep everything dry, or several plastic bags one inside the other serves the same purpose. Backpacks also provide good flotation.
CLOTHING - Volley type sandshoes are by far the best type of shoe for canyoning although there not very comfortable for long walks.Woollen socks, wetsuit and thermals. Beanie is a good idea also.
ABSEILING EQUIPMENT - Super static dry treated rope is by far the best to use in canyons, as it is light, does'nt stretch and does'nt absorb water, therefore it floats. Due to abseils being on double rope 9mm or 10mm is preferred. Length of the rope depends on the longest abseil. Ropes are usually 50m with 60m being more popular.
Harness is needed for each person, with various breaking devices; figure eight, piton bar, whale tales, pit-stop or a rack being the most popular device.
Helmets are a must, maps, compass essential. An eperb is an excellent safety tool to have cost permitting.
A little knowledge can be dangerous, a lot can be helpfull. When canyoning you should always have good safety knowlege and equipment.
First Aid Kit - Should be carried on any trip, no matter how short it is. Your kit should include items to treat, sprains, cuts, fractures and most important contain a space blanket.
Helmets - There are a lot of people out there who think that they dont require protective headwear, but from experience a helmet of some sort is a must. You only have one head so protect it.
Torch - Good idea for those longish canyons, you may have to walk out in the dark.
Matches - You may have to light a fire if caught out overnight due to injury within your party. A good item to keep in your first-aid kit.
These include prussik slings, jumars, tiblocs, etc. Everyone in the group sure have some knowledge in how to prussik. The leader sure be proficient in this area, you never know when you may have to retrieve a jammed rope, or rescue someone.