What better to do on a muggy summer evening than go wading in the river? 12 intrepid GoodGymmers from Lewisham, Greenwich and Southwark did just that on Wednesday evening.

The task was to help clean up the River Ravensbourne through Brookmill Park in Deptford, a a mile or so down from where it flows into the Thames at Deptford Creek. Years back, the river was stuck in a concrete culvert, but when the Docklands Light Railway came here in the 1990s, the DLR paid for it to be brought back to life again. So these days it bubbles and gurgles through the park - you wouldn't think you were in Deptford. It's also remarkably clean - and that's where volunteers come in.

After donning our waders and grabbing litter-picking tools, we took to the water in pairs, spreading out along the river, removing bits of builders' junk, old clothes, plastics, drinks cans, and ripping out bits of Himalayan balsam that had appeared on the banks. There were lots of dead crabs, but nothing too gruesome. The water was surprisingly deep in places, but we managed to remain standing...

While the river looked clean, we still managed to fill plenty of bags with rubbish. And wandering through a fast-flowing river with heavy waders is a surprisingly good workout.

It was a terrific evening to catch up with old faces (and new ones too - time to welcome Victoria to GG Lewisham after switching from Lambeth) and spot a few minty-fresh 100 tops too. Plenty of passers-by stopped to say hello too. Thanks to Lawrence and Tim for leading us - we'll be back (if you let us!)