How to swim longer
Althought it's difficult to admit, I need help. I'm not the greatest swimmer - not anywhere near it! I'm way past denial and well into acceptance, but now I need a path forward.
At my Oly tri a few weekends ago, I swam 1500m in 40:##...just downright pathetic if you ask me.
My first Oly back in 2004 was a 53 minute swim.
I've never got under 40mins for a HIM.
My IM swim times (started five IMs) have been between 1:30s (IMFL08, my IM swim PR) and 2:05 (IMFL06, my first IM).
I'm always within 5% of the BOP of my age group. Getting easily passed by several waves behind me.
I've been told repeatedly my technique and endurance aren't the issues, altho there's always room for improvement in those aspects. For me it's a mental block.
Ex, in a pool, I can swim no longer than 100m at a time, then I need to stop and regroup and get my breathing and HR under control. Well, what I think is my HR being out of control, in actuality it's not - I've monitored it. In open water it's even worse-I can make it about 75m before the same regrouping is necessary.
This has been the most frustating part of my tri life since I started in 2004. 
It probably is due to the fact that my brother used to torture me in the pool by holding me under and incessantly splashing me as a kid, and that I've been dragged under waterfalls a few times in my adult life and almost died (no joke, so it's shocking I can swim at all if you ask me).
I've tried everything I can think of, including visualization and even hypnotism.
I always swim with a pull buoy in the pool.
I mostly do long swim sets with a snorkel, just to build my endurance.
I'll never sign up for a HIM or longer race that doesn't guaranteed allow a wetsuit.
In fresh water, even WITH a full-sleeve wetsuit, I'll still almost sink unless my lungs are full.
When working with coaches (one-on-one instruction or classes-such as masters), they help with technique and provide sets, but cannot seem to help me with my issues.
But when it comes to race time, it's me all by myself - and I FAIL big time. 
I've overcome the "short fat kid" syndrome growing up to get where I'm at now, which I try not to take for granted. I just know I'm capable of so much more!
PLEASE HELP!!! 
Comments
Can you give some more background regarding your training(volume and frequency) and instruction experience? When you swam masters did you ever swim longer sets, etc?
It's tough one when you say it's not technique or endurance. You've also tried to address the psychological. It does seem like there is some mental stuff going on especially with your bad experiences in the water. However, simply swimming more could be the answer if, in fact, your technique is good. Have you considered a big swim block? I would call into question endurance if you never swim more than 100 at a time.
Great advice from Dewey and some thing I've struggled with before.
I agree with Dewey...
Your description of your swimming challenges mimic me perfectly for the first two years of training. It wasnt until I learned to breath correctly did i start to actually feel comfortable in the water. I went through three swim coaches, multiple classes and many hours in the pool to finally find a technique that allowed me to swim continuously without loosing my breath.
Definitely not a WSM, but wonder if the snorkel is actually hurting more than helping? I would think you would have less time to learn how to breath properly the more you use it...IMHO.
I've been doing masters classes in Dallas for several years, in both 25m and 50m pools. I also swim a lot on my own when I can't get to class. At most, a few years ago, I was going 4x/week: 2 to masters and 2 on my own (including a long swim on Sunday afternoons). I'm swimming 3x/week on my own right now, at a 24hr fitness 25m pool.
When I swam masters more often, and a long set was prescribed, I'd just break it up into manageable distances. Ex, a 400 was broken into 4x100s. Obviously not the same end result/effect, but I did the yardage.
I've used the snorkel for anything 200m or longer for the last couple years, hoping to build "in water confidence", and I can go for miles and miles with it. So the pure-swimming endurance is there, if you ask me. But I do a lot of 50m and 100m without it. When I don't have a formal swim schedule (per an EN plan), then I usually do some 50-100m freestyle non-snorkel swims, mostly fast pace work; alternating with some 200-400m long sets with the snorkel. It sufficiently smokes me after an hour.
But I see the point y'all are presenting about the snorkel. By process of elimination alone, using a snorkel and being able to go for miles would indicate that my breathing has issues.
I'll hit swimsmooth for whatever they have, hoping to learn something new. But please keep the advice coming, I'm tired of swimming like a wounded seal at the back of the pack!
You could try building up gradually. Do 125's a week ot two, 150's then next, etc.
That's what I'm doing now, building up slowly - almost like from scratch. Started with 75s again last week, to "rebuild" the base, then moving up and longer!
I have zero doubt that you have a serious mental block that leads to the breathing issues. I think that's apparent from your description of things.
I'm sure your endurance is fine as well. The person(s) that told you your technique isn't an issue probably needs a punch in the face. For the adult onset swimmer who hasn't spent the majority of their life swimming 1 billion meters at a 1:10 per 100m pace... technique is ALWAYS the issue! The topic should be titled "How to swim better" and not "How to swim longer."
While I'm certainly not discounting the mental block you have, flawed technique is certainly playing a major role in your swim issues. As David Lesh pointed out, flawed technique is probably causing you to sink somewhat or screw up a breath, which causes you to freak out a bit, which turns into full on fear and anxiety. You need to become more comfortable in the water and and the first step is to improve your technique. You're just not confident in the water because you don't think you can do it. You can do it with the right help.
I don't know how attached you are to your swim coaches but you might want to change coaches. I hate to say that without knowing anything beyond what you typed in here but it just might be time to find someone who could help you better. Not saying they suck or anything but if it isn't working then why do you still go to them?
I'm no swimming guru by any stretch. Never taken a lesson in my life but I have a pretty good understanding of my limitations in the water. I know that I have more or less peaked from a speed perspective until I get some actual instruction. It has zippity-do-da to do with fitness. Technique, technique, technique.
I'm not fast in the water, at all. MOP, consistently. I can't give you any feedback on technique, wouldn't want to make your situation worse. I still do 95% technique workouts with a very small amount of 100s to 250s.
But, I'll share what is working for me on that breathing stuff. Once I got used to bilateral breathing, I started stretching out my breathing to a hypoxic level. Breathing 1-2 times per 25m. Then easing down to every 5th stroke. I usually do drill25/hard free back with as little breathing as possible. Then, the cool down might be a few ez 25s with breathing every 3rd. So, when I go do a longer 1x set, every 4 weeks or so (maybe a race), my effort level goes way down and I breathe as often as I feel is necessary, every third or even every stroke if I press at all. Makes me feel like I can swim forever, might not be the fastest, but steady and strong ahead.
Another thing, don't discredit all that water history you mentioned. Sounds like there is a head thing going on. And, I'm not talking head position. Kudos to ya for staring it down and not letting it be an excuse to keep you on the sidelines!
I may get a fine for posting anything that may resemble a swim tip....
Chris,
That's actually good advice! We will do similar workouts in masters and I find that it helps my breathing following them. We'll do sets like 100 w/ 1st 25 breath every 3 strokes, 2nd 25 breath every 5, 3rd breath every 7, 4th breath every 9. It gets hypoxic by the last 25 for sure.
Actually have been swimming a long time (not that I am fast or a WSM, but). Have two other friends that were using a snorkle a lot to swim for comfort and panick. They were filmed swimming without a snorkle and it turned out they had almost no body rotation. I am down with one of the previous suggestions to switch coaches, and use the swim technique e-book to focus a lot of attention (very short distances), doing mostly the shoulder rotation/body roll technical drills.
If you aren't rolling using a snorkle, and most of your training is with a snorkle, you will not train yourself to breath and roll properly.
My 2 cents.
Paul
@ Matt, hate to disagree with the thread going re: hypoxic training, but that is for a different purpose -- training your muscles to continue working as oxygen gets limiting and CO2 builds-up. While that can do a little to help with body roll/position, the drills for that are more effective if the issue is limited body roll.
Scott,
Don't worry about the swim until after IM AZ. This is from one of the IM AZ Old Farts!!!
Ditto to what everyone else has said. Go to the swim smooth website. It is excellent. The urge to breath does not come from the lack of oxygen but the build up of CO2. So getting the technique of breathing properly is the key IMO. Think of it as blowing out the CO2 underwater and then inhaling when your face comes out of the water to breath. I would suspect that some of the time your mouth is out of the water, you are actually blowing some of the air OUT, when that short time should be air coming IN. The hypoxic swim sets will get you used to the feeling of panic as the CO2 builds up. You already have the mental toughness to get through this hurdle, it just a minor adjustment in technique.
I have 6 brothers so i know what you mean about being abused and tortured by your brother.