I am the same way, from what I have been told my form is good. My problem is fearing the exhale part of the swim. I have looked for tips online without much success so +2 to the breathing pointers?

I am currently training for my first tri (Aug 1) and did my first OW swim on Memorial Day. All my swim training so far has been in the pool. Since I simply wanted to get a feel for the open water, I kept it light, half a mile. One thing I changed from pool to OW was my breathing. In the pool, I breathe every 3 strokes, bilateral breathing, when I was in the ocean...ok the bay.....I breathed every stroke. It helped relax me since I am not fond of OW. It was tricky having to pick my head up quite often to sight, so that could have helped my breathing as well.

Did you do any OW swimming before the race? I guess I shouldn't assume the swim was in OW...was it in a pool?

swimming is an entirely different beast that needs work and takes quite some time to master. the breathing can be an issue even for the fittest of athletes. once in oxygen deficit it's hard to recover, on a bike you can coast, on a run your can walk, on a swim you can sink :) get in the pool a few times per week, 2 at the very least, and swim with a masters group if you have one. technique is the key.

I'm just going to hazard a guess that your technique is nowhere near fine ;-)

See, what happens is that biking and running speed and endurance are greatly determined by cardiovascular and muscular condition, whereas swimming speed and endurance are largely determined by swimming technique. And the fitter and more athletic you are, the greater your muscle density and lower your bodyfat, the better technique you have to have in order not to sink. That's why the portly grandma in the next lane over can get away with barely moving her arms, and us triathletes sink like a stone.

The absolute best and fastest way to gain the ability to swim well for any duration is to find a swim coach or a coached workout (like a Master's group) or swim clinic and work on your technique. It literally can take less than 30 minutes of coaching to go from struggling to cruising, depending on what your particular issues are.

obviously i have no idea how your swim technique is
BUT.
i always thought i was a decent swimmer. started doing the tri's at around age 28. I did many sprint and olympic distance before moving to ironman.

i specifically remember some of my times for 1.5km swim. AGAIN i thought i had decent technique but was around 97th place out of water out of 105 at a time of 38 minutes.

I took around 10 private swim lessons from an ex olympic swimmer and he stripped my technique apart. To make a long story short.......................a year later i did the same race and trained around the same amount. After the lessons my time went down from 38 minutes to 26 minutes.
hmmmmmmmmmmmm check your technique?? yes.

good luck

too add to my post yesterday.
i remember been out of breathe often. It was due to bad technique and not taking slower steady breathes. I also remember my coach shouting RELAX and said i was panting like a dog.