The king's vast holiday home overlooks the beach, where a police sign says: "Access and circulation are forbidden on this public maritime domain and swimming is banned under the right of the residence of the king of Saudi Arabia."
A French police van is parked at the entrance of the royal home, where the king and 1,000 members of his entourage arrived on Saturday.
Another police vehicle is stationed at the Mirandole beach, between Antibes and Marseille.
In the water, two police boats patrol the coastline to ensure that no intruders breach the 300-metre radius ban.
At the main entrance to the king's villa which stretches along several hundred metres of turquoise coastline, security guards can be seen relaxing on plastic sun loungers.
Access to beaches is normally open to the public in France as it is the state that owns the coast, and tensions often flare when local authorities close them off partially by granting concessions to firms offering rentals of parasols and sunbeds.
One petition demanding that the beach stay open has gathered 120,000 signatures from locals.
"The Saudis are welcome in France so long as they respect French law," said local councillor Jean-Noel Falcou, who started the petition, referring to illegal construction work by the villa.
"Where will we end up if the rich and powerful have the right to not abide by the law, under the pretext that they spend money?"
But others felt differently.
A rival petition went online Sunday, gathering some 100 signatures, calling for "support for the Saudis for obvious reasons of state security and for the economic benefits."
- 'A good client' -
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For starters, some 400 luxury sedans with tinted windows have been hired for the royal visit this month, according to a group of drivers waiting at a hotel entrance.
They will be used to drive the Saudi king's relatives and friends around, as well as military officials from the oil-rich Gulf country.
Waiting for clients at a top hotel in Cannes, where some of the Saudi guests are being hosted, one driver wearing a shirt and tie despite the damp Mediterranean mid-summer heat is sure to have plenty of work in the coming weeks.
"They ask us to take them to restaurants, or they say they want to visit Saint Tropez, Monaco, Nice or villas in the area, because they want to buy property," Aimed told AFP.
His colleague Aimen believes the king's visit "is a very good thing for the region."
Using another acronym to refer to the jihadist Islamic State group, he said: "We need to understand these security measures... Saudi Arabia is a country at war that is fighting Daesh. We don't need to throw confetti at him but if we do not welcome him well, he will go wherever they do roll the red carpet out for him."
Other locals also see the visit as a boon for the Riviera.
"The beach closure bothers me a little," said Tony, who owns an apartment across the road from the Mirandole beach.
"But I am ready to sacrifice my personal comfort because the king is a good client for France."
Keltoum and Jo, two sisters on holiday near Mirandole beach, also said the economic benefits trumped all.
"These little inconveniences pale in significance in front of the revenues. The king's presence doesn't bother us at all," they said.
"It's been three weeks since delivery trucks started arriving," transporting appliances, flowers and even domestic workers, said the sisters.
"And you should see the queues in Cannes in front of Hermes and Chanel!"