Love the London Royal Docks and Watersports Centre
At the Docks you change on the waterside in the open, with tourists passing and swim in choppy open water almost under the London Cable Car. Planes pass low overhead either taking off or landing at City Airport and hotel and bar guests on balconies overlook the water.
The staff are super friendly and helpful: my goggles pinged off my face and broke as I was on the jetty about to jump in and there was a bucket with spares to borrow. You should wear a brightly coloured hat and in winter tow floats are compulsory too.
There are routes marked by massive buoys to swim around, from 150-750m. There were lots of people swimming despite our joining the last session of the evening, and the swim back towards shore was in blinding low sun - no complaints, it was lovely!
Again, big buoys mark the routes of varying distances, and here a lifeguard sat in a kayak while we swam.
