A truly transparent sea!
Honestly, the name isn't all that attractive (it translates to Seasick Island); I suppose it is derived from the sensation of nausea provoked by travelling over the often-rough seas in the area or (more probably) as a corruption of "mal viento" (bad winds) due to the heavy winds in the area which cause massive waves which sometimes cut off the island for days at a time.
That being said, don't let the name's meteorological doom-and-gloom put you off; the island is a destination that shouldn't be missed. The waters are crystal-clear in a way that's unusual even for Sardinia, an island known for its beautiful transparent waters.