Good question! I have IMFL coming and it will be my first race in salt water. So far I have learned -
1. Not to drink the water during the swim, got it.
2. I will be a little more bouyant,, which always a good thing!
If you take in salt, you can always "use" it later in the race! (Just kidding of course)
Salt water is GREAT ! You will feel more bouyant-and your body position will be a bit different especially if you are wearing a wetsuit. But it's SO FUN!
I would only worry about it adding to dehydration if the water is above 82 degrees.
Stephan, I spend all my time training in a pool or freshwater lake. I did the half in Hawaii in June 2010, which is salt water, and that was the best swim experience of my life. I felt more fluent in the water and a lot more buoyant. Don't worry about the salt water just choose a race that you want to do as long as you train in fresh water you should be ready for anything.
I guess it's a combination of all of that yes. I realize that swimming in calm water is the same for both. From the times I swam in moderately choppy ocean water, taking water in the mouth definitely makes it more difficult. I don't like chlorine either but it is easier to withstand then salty ocean water.