swim exhaustion

Breathing is natural. Dont make it an artificial gesture.

Simply doing so will make it easier on you. Think about your bike or your run. Do you have to do anything special to breathe? It just happens naturally...

Being in the water should not change anything to this fact.

I would have a coach take a look at your form, particularly your breathing, and give you some advice. Most likely a form issue, rather than fitness. It's also possible that anxiety or cold water played a role-hard to say without knowing specifics.

I am an adult onset swimmer and the swim was difficult for me to crack having no coaching.
Many people will say time alone won't make you better but when it comes to breathing I found this is not true.

If it helps, this is what worked for me:
use 2 beat kicks (a lot of argument here but this is just what I chose)
swim a lot more, 3-4 xs per week.
Practice 2 stroke breathing if you're just using 3 and get comfortable switching it up if you wish to use 3 stroke at all.
Kickboard drills - keep one arm on the kickboard and kick at least a hundred yards each session switching every 50 or 25. It will begin to feel natural.

That should help with breathing but good technique is a whole nother story, I'm still working on.

I honestly have been struggling with the same issue at the beginning of this year. Last year I did a 1500 yrd swim for my first tri and it was a train wreck at best. The only reason I was able to breath was that I was breathing only on one side every other stroke. This is a bad habit to get into and after that I started learning the bi-lateral 3 stroke technique, which was fairly exhausting.

The reason being was my form was not good, I had no idea of things such as what the 'catch' was, or the fact that I was turning my arms like a windmill in a hurricane.

I started using a 'pull buoy' and focusing on my high elbow catch, extending long arms, focusing on my pull. Then switch to a paddle board to work on my kick. Honestly your kick needs to be somewhat in synch, but once you use the paddle board you will have to laugh at how hard you can kick and still go nowhere. Your kick is really only to keep you back end stabilized, so if your focusing too much on the kick and kicking like crazy, you are tiring your self out unnecessarily. I had to just slow way down and just focus on arm turnover, the catch and pull. Now I can feel the 'glide' and with further practice I will get much better and faster.

Today after several previous sessions of focusing intensely on form, I was able to do 2x50 yard warm ups, 2x100 yard, 2x200, 2x400, and 1x900yard. I felt great. I could feel my heart rate getting into a steady high pace like when I run, My breathing was steady, my stroke technique was consistent. I was super happy with today's swim workout, it was my best ever!

Matter fact I felt so good, I got on the treadmill and busted out a quick 5K! (Ok, so maybe the energy gel I ate prior to the swim helped a little, lol

In addition I recently learned the 'flip turn' and dolphin kick both of which help me from having to stop at each end of the pool.
https://swimspeedsecrets.com/2016/02/08/top-5-reasons-triathletes-sh...

Oh ya, I had the luck last time at the pool of watching some very talented young high school swim team members practicing laps. I will dip down in the water and watch their form and that can help verify if your doing things right or wrong.

Look up a book and workout series call 'Swim Speed Secrets' and 'Swim Speed Workout's'. The author also has a lot of online videos that are helpful.

Best wishes and cheers!

Without having looked at a video of you in the pool, my bet is that your legs are dragging in the water. This will slow you down and make swimming more exhausting. As someone above said, kicking has less to do with propulsion and more with keeping you in a proper hydrodynamic position (horizontal to the water surface). Think in terms of a boat, always faster on a plane than chugging along with the stern deep in the water. The best thing would be to get some swim lessons, but if not possible, kick board drills to get the feeling of maintaining a hydrodynamic position in the water will be essential. Do not underestimate how much core strength goes into swimming correctly.

Here are two other options whic have worked for me
1) you could be hyperventilating. Before you swim just get used to the water a bit. Very often the change in temp of the water vs air can make you feel out of breadth. The first 500 of an IM is always the hardest for me.
2) when I first started swimming - when I was 36 - so I'm a born swimmer - a blogger recommended humming while I swim. He said it would force me to breadth since I was likely holding my breadth someplace in the cycle.

Good luck.

Swimming 800m in open water is not a great way to start off. You need to break it up. 25 or 50 at a time rest, repeat. Total session can be that far but you need to baby step it.

Swimming is technical, and like running and biking, it takes fitness.

I joined a masters swim club last fall. It turned out that I did not know how to swim even though I had done some sprints. I have gotten better, relative to where I started much much better. One of my favourite comments from a coach was, "Wow, your freestyle has improved so much! I do not know how you even moved forward when you started." I thought I was doing it correctly, but not even close.

I agree with above responses. Coaching and water-time. There are also a ton of youtube videos on stroke technique, which could be very helpful.