The first thing you probably want to know about beaches in Nice is: Are the beaches clean? Is the water clean? Yes! On most mornings you'll have no trouble seeing your toes beneath five feet of water. You should be reassured to know that all Nice beaches conform to European standards and all beaches west of the port have "good to excellent quality" water.
The two beaches east of the port--Militaires and La Reserve--have had problems with water quality mainly because of their proximity to Nice port. Their overall ratings vary between "poor" and "sufficient". On those beaches it's best to keep your head above water. (source:baignades.sante.gouv.fr/)
The water of Nice's spectacular Baie des Anges is monitored weekly from June to September. If you head to the beach early you may see the small boat that takes water samples about 10 metres from the shore. The samples are then tested for E-coli, total coliforms and streptococci. The results are posted at www.nice.fr.
So much for the invisible dirt. What about floating bottles, plastic bags and other unsightly detritus? Niçois call it the "Courant Ligure" (Ligurian current) and it brings 20 tons of detritus each year. You won't see much of it though. That too, is regularly swept up by the four cleaning boats that patrol the waters from June to September.
If you watch the water regularly, as I do, you'll notice that it's visibly cleaner in the morning. That's because the nighttime currents regularly sweep any detritus out to sea.
You'll also notice that the water is visibly cloudier after a storm as water purification stations in the region overflow into the Paillon river which dumps its effluents into the sea. Many Nice residents avoid swimming for a day or two after a storm.
Blue Flag Beaches
The Blue Flag program is a program run by the non-profit organisation, the Foundation for Environmental Education (FEE). The idea is to promote sustainable development of beaches by awarding a "blue flag" to beaches that meet standards of water quality, environmental education and management, safety and other criteria.