You might try finding someone who does a lot of triathlons.
A friend of mine competes for the University of Georgia triathlon team. So I asked her to help me out with swimming which she did. It was very intense (thanks to the 10mile Mtn bike ride I did before) but I improved big time. She told me my technique was pretty good but could tell when I got fatigued since my form got real sloppy. I swam for roughly an hour. But 2 days before at my local gym I struggled to swim for 25m after just getting into the pool. At the UGA pool it was 50m and even after a very intense mountain bike ride and an hour of swimming at the end I was able to swim a full 50m with fairly good form.
You could probably find a local university and run in some of their 5/10Ks and talk to people there. Odds are you'll find a Tri kid who I'm sure would love to teach you and push you along for a little cash.