If you wear spectacles, they need to be secured to your person such that in the event of them falling off, they are not lost. Clothing Specialist watersports clothing is ideal but expensive. If you can borrow some, e.g. a long-john wetsuit, this is ideal. Alternatively, you could adapt some everyday clothing for your canoeing sessions. Wool and synthetic clothing are good because they keep you warm when they are wet.
Many thin layers are better than one thick layer.
The other essential item is to wear something to keep off the wind. A cagoule or nylon waterproof top is ideal and will make a great difference. Waterproof trousers also help a lot to keep off the cold. Do NOT bring cotton clothing to wear on the water. For example, don't bring cotton tee shirts, denims or jeans.