Direct answer
Playa Paraíso is the best public-access beach with classic Caribbean white sand. Playa Pescadores is the local move (free, fishermen-village feel). The Hotel Zone beach clubs (Ahau, Mia, Be Tulum) charge a day-use fee but include sunbeds. Skip the beach south of the National Park entrance — sargassum traps there.
Tulum's beach is one continuous strip, but access points and crowd levels vary. Playa Paraíso (just outside the ruins) is the best public-access spot. Playa Pescadores in the Pueblo-adjacent fishing area is the locals' free beach. Hotel Zone beach clubs (Ahau, Coco Tulum, Mia) charge 800–1,500 pesos for a sunbed with minimum spend. Sargassum (seaweed) is real and varies by week.
