Sometimes... Mallorca 17.6.13... Does anyone know that fish?

Just in front of the big Playa de Palma, the very turistic beach, sometimes dirty and crowded, today I found some stingrays, soles, starfishes and a weird fish... if anyone of you knows its name, please let me know by commenting this post.

As you can see it's got blu-greenish wings and crab-like legs... do you know it?

In Sometimes, Palma de Mallorca.