I can tell you now what swimming in 18 degrees Celsius (17,5, actually) feels like: bloody cold, well, what a surprise!. Skin initially burning, heart pounding, it took me 10 minutes to enter the water... And yet, I managed to stay in and swim for 4 hours 15 minutes, some 12 kms! It took a 20-minute hot shower and a truck load of food to warm up again after that. Very encouraging though, I hadn't quite expected to be able to do that on day 1 already.
Only a two-hour swim planned for today, and I find myself procrastinating, I should have been in the water an hour ago. While doable, swimming in this water temperature is not exactly appealing yet... ;-)
OK, 'nuff said, off I go now.