Here's another article from BeginnerTriathlete.com helping with swim workouts and breaking it down for the Sprint and Oly distances. Remember, if you're just beginning to swim and can't do all of the distances on the training plan, you'll build up to it.
Many of these workouts split the total swim distance into smaller sets which makes it much more manageable to complete. As a point of reference, last year when training for a the 1.2 mile (~1900 meters) swim of a half-ironman, I never swam more than 1600 consecutive meters. Generally, my workouts were broken into anything from 100 to 400m sets, depending on the workout focus.