I agree that its often temperature inversions moreso than tropo.  At least up to a point distance-wise.  On some of these 'skip events' you can watch as the the thing moves with the weather.  I don't think the salt water harms or helps from a 'salt' aspect.  Its just that these inversions often find their best conditions due to the water temperature.

My best war-story from Puerto Rico.  I was TV-DXing and hit an odd-bird in an odd (to me) language.  It turned out to be TV Apunte (I think that's the spelling) from Surinam, a relatively small broadcaster. Found it on the  web and noticed they also operated an FM station.  Went to the FM radio and dialled it in and it was as strong as any local.

I had 'skip' to YV earlier in the day but when R/TV Apunte was booming in there was no sign of any other distant signal.  The line to them was apparently razor sharp.  Lasted at least a half-hour.

Been on DishNetwork for the past 2-3 years for the local tv and the outdoor antenna has fallen into poor health.  Plus the dish guy used some of my cables (aargh).  Bought a rotor a couple months ago planning to restore my VHF DX capabilities.  Still haven't gotten a round tuit :)

-Bill