Recipe for a good revision break.

Pre fill your river to roughly “cruisy” and set in an ideal local spot.
Take one tired student, seasoned lightly with notes on chromatography, and marinade with biros and highlighters for approximately two hours.
Stir in a number of cups of tea, and allow to doze. Mix in a large bag of sweaty kit, a boat, paddles and any accessories to taste.
Place all the ingredients into the pre-filled river, and allow to flow, basting occasionally with a cheeky boof move, or rock spin.
You should find about 30 minutes is an ideal length of time to prepare your student for the next bout of mind numbing.