Towel
Shoes that don't have laces but do have a toe (water shoes are really good)
Close fitting thermal / wool top and bottoms eg a fleece jumper a size too small and trackie bottoms
Swimsuit / speedos
Wetsuit although canoeists don't generally wear them so don't go buying one specially
Jacket: lightweight windproof / showerproof jacket
Some money
ID eg driving licence
Emergency contact info to be handed to whoever's on duty that evening with id sight
Full change of clothes that are dry for when you're off the water.
You will see experienced paddlers wearing specialist clothing. Ask them about it. They also wear board shorts but we don't recommend these for beginners as when you fall out of a kayak, your legs can get knocked so long trousers are good idea.