I'm from Oleander's camp. I much prefer OW to a pool, but I find that I lose alot of intensity/speed if I swim alot of OW in training...seems like I need a pace clock keep me from slacking.
My $0.02 for being okay with OW:
1. Get bigger goggles: like the swim masks. The more you can see the less of the unknown there is.
Along that line, for the next tropical vacation you take try snorkeling or even scuba diving. You'll find that sea/lake critters are much more afraid of us than we are of them.
2. When swimming OW alone, try swimming with a rescue can or tube tied to your ankle: http://www.kiefer.com/...E44FFABBDC3C2ED16B8C
If you're swimming in deep waters and need to catch your breath you can hang on to it. Also, the extra drag will help make you a stronger swimmer.
3. The cold water usually gives me some bronchospasm when I first get in. I make sure to pee in my wetsuit to warm it up and sometimes use an inhaler before swimming. This help prevent the hyperventilation of first getting into chilly water.
Good luck! Happy swimming!!