Monday - swim training

I think I am starting to get a little concerned now, its only 5 weeks to my first triathlon. Thankfully, its a pool based swim, so I don't have any fear of drowning, but I need to get my act together. So I set off to the pool this morning for a swim. I only did 12 lengths, but they were full lengths without stopping, although I did stop at each end. I took approx 45 seconds to do each length. Has I kept it up continuously that would be 9 minutes to do 300 meters. At that pace, I would achieve the 500 mts in 15 mins. That sounds good to me, now I just need to do it - lol.