[trux]

OK, I believe you probably mean Les Martigues - at the delta of Rhone and close to Marseille. That's already a better part of the coast than the rest of the Gulf which is mainly sandy and with bad visibility. I do not know Les Martigues, but suppose it is rather shallow and sandy in that place, but I highly recommend that you take a car or even better a train (very romantic railway! And with a car you'll have problems to enter some of the villages anyway) and go to Niolon or one of the other villages on the coast in the direction to Marseille). The bottom is rocky, and you can get to interesting depth (+20m) immediately. It is one of the most beautiful parts of the French coast. There are even corals, which is rather unusual in this part of Med or in Med in general). Also the water temperatures are much higher here than deep inside the Gulf of Lion. As for spearing, I cannot advise you, but you'll find plenty of threads about spearfishing regulation in France, here on DB. And as anywhere else in the Med, do not expect plenty of big fish. However, since you are located in Spain, you probably know that.