I love Hyeres islands. I went there 5 times during the '90s even a liveboard. IIRC it's the oldest MPA in Europe.
Speaking of short range destinations May I suggest a couple of other destinations in Italy worth to consider?
Argentario in Tuscany. There's a national marine protected area much more as Portofino but cheaper and with better visibility. (www.argentariodivers.com is one of the biggest and most professional diving center in Italy). Give me a shout if you come!
Strait of Messina. Scilla is a classic destination. During the '90s it was considered the best dive spot in the Mediterranean sea. I'm still convinced that it is. Maybe not the best but among the 3 best med dive areas. Why it's not so famous? because it's in Calabria, perhaps the most underdeveloped Italian region. But the dives there....
Strait of Messina deserves a special explanation.
The particular morphological conditions of the Strait (in the narrowest point it is only 100 meters deep but in the southern part it quickly reaches over 2000 meters) make it possible to form a venturi effect with strong currents that bring nutrients from the depths. It is an extraordinary ecosystem, unique in the Mediterranean Sea for biocenosis and abundance of species.
The intense and alternating currents determine a condition of "Atlantic" type. In fact, many purely Atlantic species, such as laminaria, although present in some other areas of the Mediterranean Sea, only in the Strait of Messina are able to form well-structured communities forming real underwater forests.
Another peculiarity of the Strait of Messina is the presence of a numerous abyssal fauna which, transported to the surface by the current, can be easily captured or found beached along the shore. Their abundant presence attracted to Messina between the second half of the nineteenth century and the beginning of the twentieth century scientists from all over Europe who could find, in a relatively simple way, the most varied and abundant material for their studies. Krohn and Anton Dohrn, defined the Strait of Messina as the paradise of zoologists.
Basically you only dive at times of tidal fatigue. The water is warm and visibility never drops below 20 meters. Even in the middle of winter I found minimum sea temperatures of 18 degrees Celsius. Just google "reggio calabria lungomare alberi" to understand the climate there.
Many dives are done from the shore and you can meet very rare species for the Mediterranean. If you search for "trumpet fish in the Strait of Messina" you will understand what I mean.
If you like wrecks you have no choice but to choose including some that can be reached from the beach. One of the many
It's hard to find conditions where you can't dive there. You also have the Sicilian coasts at your disposal.
The prices are outrageous and you have the airport of Reggio Calabria to 10 minutes.
A famous diving is the Scilla Diving Center
Check this out to see what kind of photos are taken in the Strait of Messina.
Don't mess with currents here!