Sub-aqua archaeology

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The smell of the river
The river Wandle runs right through the site of the Time Team excavations at Merton Abbey Mills. Not wanting to miss anything that might lie underwater, Time Team called in top diver Gordon Bell and some of his colleagues from the Mole Valley (www.mvsac.org.uk) and Meadhurst (www.mesac.co.uk) Sub Aqua clubs.

Though it has its own distinctive smell, the Wandle has remarkably clean waters. However, the river bed is littered with the debris of London life covering hundreds of years. Even pre-Victorian dredging failed to eliminate evidence from earlier periods. Time Team hoped that by using experienced divers it could find important archaeological remains that would otherwise remain undiscovered.

A passion for diving
'I've been diving in this river for 26 years,' says Gordon Bell, 'We go to different spots every Sunday – it's just a passion. I've recorded every dive over all that time and know where every find has come from. Most rivers have been heavily dredged over the years to clear them out, but the Wandle appears to have been left alone for the last hundred years. We've found medieval lead tokens, Georgian coins, belt buckles and all sorts.'

The flow of the river keeps silt to a minimum and after heavy rain the clay bed can be seen. With the currents frequently changing speed and volume, the river provides a mixed environment for archaeological remains. Artefacts can be remarkably well preserved in fresh water, but the constant movement of the water means there is no such thing as an ordered stratigraphy, making it possible to date and place finds in context, as there is on dry land.

A big washing machine
'You need to think of the currents swirling around,' says Gordon. 'It's like one big washing machine. You can find a Victorian coin and then sealed in the clay bed below it can be a modern 50-pence piece. We record all the finds by superimposing a grid over the river bed and plotting them, or in difficult situations we measure where they're found in relation to the bank.'

Working with Time Team
So what's it been like working for Time Team? 'It's been pretty good,' says Gordon. 'We've been left to get on with it. We haven't had a great deal of rain in the last few weeks, so the flow of the river has been down. This means that much of the bottom is covered in a fine silt. Visibility is good however, so what you do is lie with your head into the current and waft your hand over the surface. The silt gets carried down stream and you can still see what you're doing.'

Time under water
How long can the divers stay under the surface? 'That's a common question that divers get asked,' says Gordon. 'A set quantity of air in a cylinder can last different amounts of time depending on how deep you go. The deeper you go the more pressure, or atmospheres, you have to breath in. The deeper you go the more oxygen you use. Because we're only just below the surface on this job, the oxygen tanks we use can last about three hours, so we can have plenty of time down there to have a good look around.'

Dodgy stomachs
As the divers work, they still get some water insider their suits. While standing around in the water they also let their demand valves (the mouth-piece they breathe through) hang at their sides and bob around in the river. Do the divers end up with dodgy stomachs from ingesting river water?

'It's actually not that bad.' says Gordon, 'There's a sewerage cleaning works upstream and all of the water here goes right through it. It's actually very clean for a London river – about twice as clean as the Thames. I don't think any of us have ever had bad after effects.'

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