At the entrance to each beach, you'll find a billboard where the beach rules are posted.
No Diving from the Jetties
(€38 fine)
No Fishing or Spearfishing from the Beach
In fact, rod fishing is tolerated if discreetly practiced early in the morning or off-season. Spearfishing or any explosive device to catch fish is severely sanctioned.
No Blocking Beach Drains
This would apply to the areas where the Peillon and Magnan rivers meet the sea at Centenaire and Magnan beaches.
No Fires
Bonfires and grills are prohibited (Fine €38)
No Access between 10pm and 7am
This rule is enforced spottily unless one is clearly camping on the beach which is strictly prohibited (€1500 fine).
No Dogs
Bring your canine friends to La Lanterne where they are welcome.
No Vehicles
Except for wheelchairs on handicapped access beaches.
No Disturbingly Loud Radios
No Soap, Shampoo or Detergent
Your beach shower is rinse only.
No Leaving Debris on the Beach or in the Sea
Obviously this includes the remains of your meal but it also includes spitting! (Fine €35)
Don't take a galet!
They are not souvenirs and you risk a fine of €38.
There are no naturist beaches in Nice; "decent dress" is required but toplessness is permited. Bathing suits are confined to the beach. Strolling the Promenade des Anglais in a bathing suit can earn you a fine of €38.
No sex on the beach. It's considered exhibitionism and incurs a fine of €15,000 or prison.
Drinking alcohol on the beach is prohibited between 8pm and 5am. If you're planning an evening picnic, be most discreet about your bottle of rosé. (Fines between €17 and €38)
Vendors are limited by a web of regulations and thus, sparse. In the summer you can buy the local paper, drinks and coffee on some public beaches but that's it.
Smoking is, for now, permitted on all Nice beaches except two: Centenaire and Lenval. But please, put the butts in the trashcans.