Go swimming in Hyde Park’s Serpentine lake

Next month there is to be a mass swimming event in the open chilly waters of Hyde Park’s Serpentine lake.
Normally, swimming in the lake is only open to members of the local swimming club — who famously take a dip on Christmas Day — but on Saturday 18th September, the general public will be allowed in as well.
Personally, a lake is something to decorously drift across in a boat while holding a gin and tonic and watching someone else do all the hard work, but I understand that t