Balance drills

I am trying to improve my balance and confidence in my ski so I have been doing some drills. I am paddling the cold, slightly dirty canals around where I live so I would like to stay in the ski as much as possible, this however limits the balance drills that I feel comfortable doing. When I am out at sea and not that bothered about falling in I can do some more exotic drills like sitting on the back deck or doing 360° turns in the seat but on the canal I am left with just 2 drills: paddling with a rest when my paddle is out of the water and paddling on one side.

Do you know any other drills that I can do that don't involve getting wet?

A friend keeps saying I should try paddling with my eyes closed but I will save that for the sea.

Paddling motions without a paddle in your hands. This is obviously a static drill.

Miss every third stroke. Try doing this for a while and remaining smooth.