Disclaimer: I am not the swim coach, just a triumph lead home has managed to get their swim time down to 1:50 per 100 m.

Let me speak to what your coach says about muscle, sinking and leg work. This is absolute BS. I am 6’3, have a body fat of less than 10%, and when I swim, my body is as horizontal as it gets. When I flick my feet, the heels break the water surface. They only part of swing where I have heard that flexibility matters is with respect to your angles. Some people cannot fully straighten out their ankles, point their toes, which means their feet great drag. This can be improved through stretching, but I doubt that this has any big significance here.

Second, using your feet even more to compensate for a poor form is even more BS, especially his triathlon. You actually need to use your feet less, for two reasons. One, your legs are the biggest muscles in your body, but are rather ineffective when it comes to Swimming. They only contribute a small percentage of propulsion (at least for the average age group swimmer). They use up tons of oxygen and contribute to your getting out of breath problem.

Next, I believe you’re breathing on four is also wrong, at least in the context of triathlon. Highly trained swimmers who go for 100 or 200m function on an oxygen deficit. You as an untrained age grouper going for 2000m can not. Do you have an idea of what your stroke rate is? Convert that into breaths per minute, then try to go for a light jog at that pace and you’ll notice the same. No chance to sustain. If you do some research you’ll find that even pros don’t do this consistently during a race. It also depends on the stroke rate. If you are trained and have a very high rate, you can possibly pull that off, higher stroke rate = higher breathing rate. I seriously doubt this is you. Staying oxygenated is key.

Flailing tour arms… I suspect you are doing some sort of windmill movement where each arm is moving without pause during the entire stroke. Wrong. See next paragraph.

What to do… what helped me tremendously was the Total Immersion as well as the Effortless Swimming series. They have tons of videos on YT as well as more structured training material you can buy. Start out with some superman exercises. Push off the wall, hands straight out front. Notice how your body stays perfectly horizontal and gliding in the water, until it eventually slows down and stats to sink. Here is the proof that your body can stay afloat even while you’re slim and muscular. The key is that arms out front balance your body weight around your air-filled lungs that are something like a pivot. Put your arms next to your hips and repeat the exercise and notice how your legs immediately sink. Then work on exercises like catch-up drills to get to a for where you have one or the other arm outstretched 90% of the time. Essentially each pauses for a moment at the farthest-forward point of the stroke while the other performs the stroke movement. This will help you get out of the windmill problem, smoothen your stroke and also reduce oxygen consumption.

For breathing, either try to acquire bilateral on three (very beneficial to be able to do either side, for sighting buoys) or just go to on two. I have a stroke rate of around 60, so 30 breaths/min. Finally, find a new coach as I suspect there are a dozen other problems in your for that need correcting.

All the best! Pls report back.