Another one from WBB! Brilliant place - having to seek donations to afford pandemic mothballing (can't be let out as a venue at the moment) so if anyone else has fond memories, do think about bunging them a tenner
Incredibly dangerous to swim in the tidal Thames, especially in central London where it's really strong. Plus there are oodles of other hazards in the river, such as the other boats (including moored ones which can suck you under, because of the current - scary and probably lethal).
Weils disease mentioned in WBB briefing, but also told its incredibly rare in tidal Thames (salt, rats avoid it) but we all need to know about it because we might go to other waterways or further up the Thames.
And yes to shit after rainfall when it all comes out of the sewers. WBB sometimes has to suspend kayaking and sailing because if water quality (power boating can sometimes continue, because you're much less likely to fall in)
Plus the amount of crap that has ended up on the river bed over the years, and gets moved around by the tide. I'd say you should be wearing something with a sturdy sole before stepping in to the water at all. But unless you have some good riparian reason to go in, then don't just don't