Where can you dive and see saltwater floating on top of freshwater causing a visual phenomenon?

Question

Thank you for estuary... wasn't exactly what i was referring to but i didn't explain as clearly as I should have. About a year ago I seen a show on Discovery. a gentalman was cave diving and entered an area where it appeared that there was a seperation in the water in the cave where the fresh water the man was diving in was not mixing with the water below it due to the fact that the salt water below was so dense he was unable to go farth in depth and enter it. I dont recall the show and it lingers on my mind that it intreged me. I was wondering where this took place or if any one else has seen or heard of this phenomenon. Appreciate your time.

Answer 1

An estuary.

If you are unsure what this is I gave you some info on it with locations. http://en.wikipedia.org/wiki/Estuary