Improving Swim Endurance

L-e-s-s-o-n-s

Beyond that:

Keep your head in the water, ROTATING to breath.

Slow down.  

Think of swimming laps like going for a "walk in the park."  Nice and easy.  You can probably walk all day, but only sprint all-out for 20-30 seconds.  Swimming is the same.  

Lessons will teach you things like proper balance in the water, kicking, breathing, body rotation and proper catch and pull technique.  My guess is that you have 1 or more of these areas to work on.  Most folks have trouble when they first start out because they are trying to go too fast.  You might want to consider whether you have these other fatigue-causing issues. 

1. kicking too hard and too wide.  For most distance swimming, the kick is de-emphasized since it provides little propulsion versus the amount of energy expended.  It's mostly used to maintain body position and assist in rotation.  In other words, keep your kick light and you'll be able to go farther.  

2. holding one's breath when their face is in the water (should be exhaling as soon as the face goes back in the water). 

3. holding head too high (this tends to drop the hips/legs which in turn creates a lot more drag to overcome).

4. swimming with a straight pull rather than with early vertical forearm (EVF) technique.  A straight arm pull feels powerful but it's taxing and effectively disappears even among elites when you get above sprint distances.

There's two identical threads so I'll repost what I wrote on the other one -

As a beginner it is a reasonable certainty that you have little swim fitness, however you likely have a bigger limiter than your fitness.  Swimming is highly technical.  At this point in your swimming career, you are probably "beating the water into submission," rather than swimming.  If you have poor technique you will have a very difficult time building fitness and becoming a faster, more efficient swimmer.  

The very best thing you can do is to get some lessons.  Spend some time with a qualified coach/instructor and learn the fundamentals, then progress to swimming freestyle.  It's valuable to learn all four of the competition strokes but since freestyle is the fastest stroke, that's the one you will be focusing on.  You can possibly find a coach or instructor at the local YMCA, perhaps a local swim team.  Absent those options, there are countless videos on-line that can help.  the problem with videos is you won't know if you are "doing it right."  Having "eyes-on-deck" in the form of a coach or instructor is the surest, fastest path to swimming with proper technique.

Swimming technique and swim fitness are two sides of the same coin.  You can't have one without the other and thus, must be developed simultaneously.  As you begin to learn and swim with proper technique, you will begin to build swim fitness based upon that proper technique.

When you begin swimming actual workouts, 16 x 25 w/20-seconds rest is better than 1 x 400.  During the intervals you will be resting so you can maintain proper technique.  During the 400, your technique will break down due to fatigue.  You want to store proper technique to muscle memory - doing intervals allows you to do that.  As you become stronger, you can add repetitions or change the length, i.e. you could go to 10 x 50 or 20 x 25.  As you continue to get stronger (and faster) you would continue to lengthen the workouts.  You DON'T need to do long continuous swims in training.  If you feel the need to do an occasional long time trial so you are mentally confident you can swim the distance, that's understandable.  However, long swims in training create problems - your technique WILL break down during a long swim.  Remember - you want to store proper technique to muscle memory - doing long swims does the opposite.

Hope that helps.