The depth of the River Thames varies along its route. At low tide at Woolwich its depth is about 6.5 metres and at London Bridge its about 1.5 metres.
The Thames has been embanked and narrowed alot since the Romans settled here in around 50AD. In Roman times where Tower Bridge is today, you could walk across the river at low tide and it would only come up to your chest.
The Thames is 215 miles long from source to estuary, is the longest river entirely in England and the second longest in the UK (after the River Severn).
The Thames varies in width along its course, its 265 metres wide at London Bridge, 448 metres at Woolwich and 732 metres at Gravesend.