I'm currently training for a half IRONMAN this summer. Last fall I completed a six week swimming lesson course and since January I have been swimming twice a week for 45 minutes each night. I've been doing intervals of 100m with 15 seconds rest between intervals.
This past Saturday I did my first "benchmark" of my progress and did lengths non-stop for an hour straight. I managed to swim 40 lengths (50m) in an hour (2km!).
I've progressed enough that I'm comfortable in the water and can do a significant distance, so what I want to do now is focus more on increasing my speed/efficiency so I can do more distance in that same hour.
I'm still pretty new to swimming and I don't have a coach - I just make up workouts for myself. So far I'm thinking of keeping my 100m intervals but alternating really fast/hard ones for "normal" pace ones. Comments? How do you train to increase your swimming pace?