As I understand it, y (“and”) in Spanish changes to e only when it precedes the vowel sound i- or hi-.
Why, then, is Rolando Villazón’s new album called Cielo e mar and not Cielo y mar? The title is in Spanish, right? He’s Mexican. I had thought the title might be in Italian, but “sea” is mare in Italian, not mar.
Never mind, looks like it is in Italian after all, named after an aria in La Gioconda which features on the album. Still a spelling mistake if you ask me, though - mar ain’t in any Italian dictionary I can find!
You may wish to take it up with Arrigo Boito, the librettist for the opera La Gioconda. 
My impression from living in Mexico is that whatever the offical grammar prescription is, the actual usage of y, e or even i (with a diacricital I don’t know how to render here), is pretty arbitrary, tending towards “y with everything”. For example, “padres y hijos” (“parents and children” or “fathers and sons”) is probably more common than “padres e hijos”.
JRB
It’s pretty common in Italian to drop the final vowel or even entire syllables. It can be part of a regional dialect (the Venetian dialect is prone to this - that’s why you have the Ca’ d’oro in Venice, and not the Casa de oro as it would be called in proper Italian), or poetic license if the author needs to shorten the word to fit the rhythm.
Only for people who haven’t realized how bad it sounds. Usually those same people think that the plural of “el águila” is “los águilas” or, conversely, that the singular must be “la águila” and those of us who say “el águila” don’t know our grammar.
The reason to say “padres e hijos” or “el águila” is that it’s easier to pronounce correctly and without mushing the words together than the regular version. To pronounce this one correctly, you need to mark a stop that isn’t a part of normal phrase flow.
I’ve encountered the over-regular versions much more often in writing than spoken, although just last week a reporter on Spanish TV said “los aguas”. It’s just a case of “overcompensated poshness”, same as the people whose dialect of Spanish doesn’t distinguish S from Z and who write a Z/C where an S should be (Hortencia instead of Hortensia).