First and foremost there is an appropriate time to tow and not to tow. If it can be avoided it is best to do so. However YOU may choose to use a tow system to move a boat across a piece of still water. As with all things of this type it is down to the paddlers own assessment on the day and therefore at the paddlers own risk. Choosing the right kind of towing option for the right conditions is critical.
These images show a paddler using a sling and carabiner to tow a boat back to its owner. The sling could either be formed from a piece of climbing tape tied appropriately or could even be a pre-sewn sling or the new Palm Snake sling.
The sling has been clipped into the boats grab handle using a large carabiner and the sling has then been slung over the paddlers arm, note it has not been put over the paddlers head. To release from the system the paddler must let go of the paddle (left hand in this case) and drop the sling off his arm.
In fast moving water or in areas where a pin is a hazard it may not be possible to quick release.
I have used this towing option and have seen this technique used many times over the years. Awareness of what is around you and good judgement is key.