Heart Rate Monitor for Swimming?

I'm using swimming as my main source of exercise and I would like to know my heart rate/caloric burn... i'm finding that you need to get one with a chest strap for best results. can i wear these in the pool under my swim suit?

any swimmers out there have HRM recommendations?

I tried my brand new polar HRM today.  It seemed to measure cycing and running fine, but wasn't picking up heart rate in the pool. 

Any tips, folks who use Polar HRMs for swimming?

I bought a reebok one on woot.com and it says the chest strap isn't waterproof, but it totally is! I've used it at least 10 times in the pool and no problems whatsoever, i'm surprised it works, but it does!

here's a link to it on amazon.com:

http://www.amazon.com/Reebok-Precision-Traine r-XT-Monitor/dp/B0012RMZ6C/ref=pd_bbs_sr_4?ie =UTF8&s=electronics&qid=1217208315&am p;sr=8-4

I have a polar F11 and I use it extensively in the pool -- I've had no problems.  REads my heart rate and logs my calories burned