[spaghetti]

Yep: max 5 kilos plus a single fish bigger than that for each person, max one grouper per day. If you exceed, the bounty is 1.032 euro and your gear is confiscated: careful!
Garry, Firenze! That's landlocked! However there's plenty of good spots in Tuscany from Livorno to Argentario within one or two hours drive from your school. If you have some extra cash for ferry and camping, you should tre Isola del Giglio, an island off the Tuscan coast, one of the best spearing places in central Italy. It's gonna become a Restricted Sealife Sanctuary next year, so you should try to make a visit there before spearfhishing becomes illegal on the Island.
Be lucky!