sebach
Contributor
You can definitively dive without a drysuit. Water can be much warmer at depth than 13-15°.For diving, the easiest is the Southern (Mediterranean) coast. Best places are from Marseille (my personal favorite) and all the way eastwards to Nice (La Ciotat, Hyeres, etc). Marseille is 3h30 from Paris by fast train (TGV). From April to November you can dive there (like most French divers) with a full 7 mm wetsuit (or semi-dry) and a hood ; drysuit is not mandatory. Water is around 11-13°C in winter at any depth ; and around 13-15°C in summer below the thermocline which is usually at 20 or 25 meters (water temp usually 21 to 24°C in summer above the thermocline).
I verified on my dive manager, and I've dived up to early november with water in the 18-20°c range, even at 60m. in September/october, the thermocline is often around 55-60m. On the other hand, if you're unlucky, with heavy winds, you can also have a 16°C water at the surface in summer.