The French Riviera water quality has always been a topic of much concern and discussion. The Mediterranean Sea is only connected to the rest of the world's seas and oceans through the narrow Strait of Gibraltar. This means that it's more vulnerable to pollution than other, more open seas.
There are some 85 cities with a population of more than 300,000 inhabitants bordering on the Mediterranean Sea, most of which have a large additional tourist population.
All of this means of course that there is a very serious risk of pollution.
The countries bordering on the Mediterranean are continually trying to reach agreement on how to prevent and cure this pollution problem, but as one can imagine, not always very successfully. Not all water flowing into the sea is properly treated, and there is a large amount of plastic debris floating around.
Despite the ongoing concerns, over the years great improvements have been made regarding the bathing water quality of the French Riviera beaches. Each town and municipality now takes great pride in ensuring their beaches and water quality are without any issue.
Yearly reviews are done and each town wants to get a so called Pavillon Bleuor blue flag, indicating the highest level of water quality. In 2012 19 towns in the Provence-Alpes-Cote d'Azur region received such a prestigious award, among them are Cap d'Ail (Monaco), Nice, Antibes, Cannes and Sainte Maxime.
Local towns and municipalities patrol their coastlines and heavy fines are imposed on people found polluting the beaches or the water.
The complete overview of bathing water quality in France can be found on the official website of the French Ministry of Health (also available in English).
Because the Mediterranean is nearly closed off from the rest of the world's oceans, there is little tidal movement - so little in fact that it is hardly noticeable. This also means that strong currents, as usually seen near the coastlines of open seas, are not present.
Having said that, we're still talking about a proper sea, a large stretch of water, so locally there may be dangerous conditions, in terms of storm winds, currents and waves.
Waves up to 10 metre (some say even higher) have been reported during storms; most of the time though the sea is calm, with wave heights less than 1 metre.
Check out this web site for up-to-date detailed marine forecasts for the Mediterranean: www.eurometeo.com .
From time to time there are large numbers of jelly fish appearing in the French Riviera coastal waters. Their sting is quite painful and you don't want to get caught up in a large shoal of them!
Usually warnings are given in local news papers and are signposted on affected beaches. Some towns and private beach owners resort to installing safety nets, which provide a 20-30 metre wide zone of safe swimming.
In the summer of 2012 a web site was set up by the University of Toulon, aiming to give a 48 hour notice of jellyfish threatening the French Riviera beaches (covering the coast from Marseille through to the Italian border): meduse.acri.fr (in French).
Although there are sharks in the Mediterranean Sea, they very rarely venture near the coast. Almost every summer there is a reported sighting of a shark, somewhere near a French Riviera beach, but those sightings seem to never get officially confirmed.
I'd be more worried about those jellyfish than about sharks when taking a dip in the sea!