Swimming the 2.2KM course against the flow of the Thames from Temple Island to Henley with a 4.30am start time means that you begin your race in the dark - the course begin lit by two green lasers - and complete it in the morning light. The setting is spectacular and identical to the Henley Regatta Course(I'd recommend that you look up the Henley Regatta youtube channel as you can see the course in all its glory). Jeremy Laiming and the team at the Henley Swim Series run this event superbly.  From the moment you arrive at the event you are smoothly guided through registration, bag check, briefing etc. I swam in the Traditional section - no wetsuit - and extra care was taken to ensure that we had warm gear at the finish. Conditions vary wildly depending on how much rain we get in June (this year we had a gentle flow - last year a torrent) so times will vary accordingly.  Some swimmers go down the night before and camp - others go with the early morning drive.  I went for the latter - it was worth the early start.