Thanks for everyone's advice.

My problem is not really getting through the swim workout- it's getting to the pool in the first place.

I wasn't really planning on doing the breaststroke for the entire race- more like alternating- I'd need to freestyle at the mass start- but I was thinking in the middle when it gets lonely and I can't see the next buoy well- maybe it would be time to switch things up. (And keep in mind, most of you would not be in any danger- I tend to finish the swim well behind almost everyone- the only advantage is that I get to spend the rest of the race passing people.)

So I did an experiment at the pool tonight and the end of the workout- all times are for 25 yard distance.

Breaststroke: 29-30 seconds
I did this 4 times, felt very consistent- was 30 seconds on the first 3 then tried to go just a little faster on the last one and hit 29 seconds.

Fast crawl: 27-31 seconds
Going all out twice. I did the first one at 27- but it was totally not sustainable, I got a massive foot cramp, and the following time could only manage 31 seconds.

Moderate crawl: 33-35 seconds
This was a pace I felt I could sustain for a longer period.

So what's wrong with me that my breaststroke is so much better than my crawl? Are there any implications of doing the breastroke for a more sustained distance? I suppose I need to repeat the experiment in open water over a longer distance.