Tiny shrimp from the Mediterranean

Hi folks!

I'd be very interested in your help to identify this tiny shrimp which i met for the first time some weeks ago, in Antibes waters (South of France).

To give you an idea of scale, she sits on some sort of gastropod (the yellow guy in the shell) which itself was climing a posedonia seaweed, which was around 1.5 cm, max 2 cm in width i'd say.

Encounter was during a night dive, about 10 meters deep.

Photographed with a Nikon D300s, some cropping but not too much.

cheers

Nicolas

Remark: i've reduced the picture size to upload it, but you can find a bit larger file here:

https://picasaweb.google.com/lh/photo/1M4qvoHtyWHcXTDd_gIiStMTjNZETYmyPJy0liipFm0?feat=directlink

Well, thinking twice i shouldn't infer it's a shrimp. The idea cross my mind that it could be a larvae of something else, lobster maybe?

It was photographed in March 2016, water about 15 degrees celcius, if it helps to identify it.