Hi Annabel – take a look at the Citizen Science Investigations intro leaflet that I’ve attached. On the last page it shows how to make a sampler from a plastic milk bottle and bamboo cane. It is an idea we borrowed from Freshwater Watch. Works fine for our CSI volunteers – thoroughly rinsed of course and rinsed before each sample.
If we’re sampling from bridges I just use a small bucket (a 2l paint kettle is ideal) on a length of rope.