Originally Posted by Humboldt

If you're brand new to swimming or haven't been in the water for a while, try a pretty basic mile ladder.

You are going to swim the following lengths (e.g., 1 means there, 2 means there and back, etc.), and want to rest 5-10 seconds between segments.

1
2
3
5
6
7
9
9
7
6
5
3
2
1

When you get finished with the ladder, you will have swam a mile.
This should take anyone who is in decent shape roughly 20-30 minutes at a comfortable pace. Since you are building up, don't feel like you need to warm-up. Just get in and swim it. This is a great way to determine if swimming is something you want to incorporate into your weekly routine.