Tubing – the art of sitting in the inflated inner tube of a tyre as it hurtles downstream, battered by the wild currents of the Bohorok – is popular though not without risk. The tubes can be rented from almost anywhere in Bukit Lawang. If you’re not a strong swimmer, consider tubing on a Sunday, when the locals employ a rescue team along the more dangerous stretches of the river around Bukit Lawang. The rapids can be quite extreme after heavy rain, so should be attempted with caution if you are without a guide. There is a bridge 12km downstream (2–3hrs) of the village, from where you can catch a bus back.