Tahiti Beach is essentially the northern tip of the very long (in full, 5 km) stretch of beach on the St Tropez peninsula called Pampelonne Beach between the Cap du Pinet and Pointe de la Bonne Terrasse.
La Plage de Pampelonne is famous for its beach clubs such as Nikki Beach, Club 55, and others where plush mattresses and cool drinks line up facing the Mediterranean.
I like Tahiti Beach but it is less glam than its adjacent sister on Pampelonne Beach. Tahiti's beach restaurants are more down to earth than the bigger names further south.
Like all beaches here, Tahiti Beach offers a free section of public beach. The public beach sits between the private clubs, the larger free section being south of Tahiti Beach, the club. You can spot it on the map below. No one will offer you a beach mattress & parasol on the free section, but no one will ask you for money either.