Every day in Krabi's Maya Bay, up to 40 blacktip reef sharks swim in the sea while about 4,000 tourists visit its white-sand beach.

Shark numbers have improved since most driven from the bay by tour boats and tourists keen to see the spot that was made famous as the set of Leonardo Di Caprio's 2000 film "The Beach".

The sharks returned after a tourism ban and the Covid-19 pandemic between 2018 and 2022 halted all visitors to the bay.

Authorities allowed limited tourism to resume in 2022, and now conservationists say shark numbers are falling again, leaving Maya Bay struggling to strike a balance between preserving its ecosystem and sustaining livelihoods with tourism.

The Maya Shark Watch Project uses underwater cameras and drones to count sharks and observe their behaviour, feeding areas, and breeding patterns. In the year between November 2021 and the end of 2022 it saw decrease in the number of sharks as tourists returned.

Several factors affect the sharks around Phi Phi Leh Island, including seasonal movement patterns and human activity like fishing, the project team said.

Under pressure from tour operators, authorities reopened Maya Bay in January 2022 but with some restrictions.

Tour boats must dock on the other side of the island from the beach; visitors must walk to the beach; the number of visitors allowed every hour is capped at 375, and they are allowed to go only knee-deep into the water.

A blacktip reef shark at Maya Bay. (Video: cprapat)