On my way to work this morning I was suprised with this sighting of something on the horizon that shouldn't be there.
Aparently it looked like a big island but...there's no island on that location...
Then I thought it could be a boat but it was far too big to be a boat, even an aircraft carrier or a tanker.
A cloud maybe...but there was a big contrast between this thing, looking solid and rocky, and the type of clouds this morning which were well above the line of the sea...
The thing seemed not to be moving and it was constant as I made my way along the shore, changing shape and size as I progressed from North to South.
And then it started disappearing smoothly until there was nothing left there...
Any idea of which kind of illusion I and the ones with me may have witnessed?

I'm going to guess it was some kind of cloud bank, very far off.

It looked pretty solid, thought about a fog bank also...but the thing looked really like Endeavour on a clear day...
Something like this:
http://homepage.mac.com/patholleran/ParkVi...ands/ci-040.jpg

Here is a link to a photo of a mirage. Even where no island is present (directly behind the boat) the mirage still appears as a dark reflection of the ruffled sea surface beyond the horizon.
http://www.hauntedamericatours.com/ghostst...LAGE/mirage.jpg

thanks ngunn, this thing was very well spotted and compact in the open sea, like a chunk of land let's say...2kms wide at a 20kms distance from the shore, I'm taking the Berlengas island as a reference since I can spot this one from where I live.
It was something like this shot I took but with less detail, damn! why didn't I had the camera ready today?...:
http://www.facebook.com/photo.php?pid=1095...p;id=1311707986

Do you mean it faded, or it shrank - or both?

It faded, in a minute or so it had completely disappeared.

...a metaphor for something?