The other day I ended up swimming further than the ironman swim distance (3.8k or 2.4 miles). I merrily swam 4k in 1 hour 24. Very happy with that. I did the 3.8k distance in 1.19 which bodes well for the ironman.
I understand that swimming in a pool is easier than in open water because in the pool you can see, there’s no current, the water temperature is good and you get the advantage from pushing off at each end. But in open water you’ll often have the benefits of a wetsuit to help so perhaps there isn’t too much difference.
A wetsuit helps your buoyancy and helps the water flow better over your body which reduces drag. Richard Hammond’s programme last Monday on BBC1 showed in slow motion photography how water distorts a human body when it’s swimming. You could see the skin and fat rippling and dimpling as the water passed over. Contrasted with the firm skin of a dolphin, you could see why swimming is relatively hard.
Let’s hope my new wetsuit (an Orca Alpha) toughens up my skin in all the right ways and makes up for the lack of pushing off to be had in lakes, sea and canals!