From St. Katharine's Dock, opposite the Tower of London, there's a nice walk to Tobacco Dock or even further, to the Shadwell Basin. For the curious, it's a good way of seeing Thomas Telford's London, and appreciate London's industrial and naval past. Passing behind houses, along a sunken canal, you usually see joggers and people out for a walk. It's a shame Tobacco Docks are closed now, but the 'pirate ships' outside are worth seeing.
From here, carry on to the peaceful Shadwell Basin; turn left to join Cable Street; or turn right and follow the Thames back to Tower Bridge. The streets around Wapping are especially intriguing, and there's a really good Italian restaurant (Il Bordello) on Wapping High Street. If you're not sure of where you are, you can always retrace your steps and the canal will take you back to St. Katharine's Docks.
From the Tower Hotel at St. Katharine's Dock (nearest tube station: Tower Hill), cross the footbridge and join St. Katharine's Way. At roundabout, cross road to reach small reservoir. Down steps and under bridge to join canal. Follow, and just after pirate ships, turn right on Wapping Lane. At the river, turn left onto Wapping High Street. Continue and this will take you back to the roundabout, where you cross over to get back to St. Katharine's Dock.
Is this your business?