An interesting question from Chicago Sandy on this blog ...
"I know that salt water = high buoyancy = faster time, but wondering if anybody has done both and would like to comment."
I would say anything that improves a swimmers buoyancy will result in faster times, as less energy is wasted maintaining the swimmers body position on top of the water
Swimmers in salt water, or wearing wetsuits, or with more body fat (or lower bone density) will float better
The extent to which a times will improve in salt water vs. fresh water will vary with a swimmers body shape and technique
I am fairly unsinkable in the ocean. I haven't yet figured out why
I might throw it over to one of the swimming nerds on this forum to explain the science