Watch: Thousands of sea turtles come to shore in massive arribada

Thousands of sea turtles came ashore Sunday in the latest arribada, a mass nesting that can last several days.

Watch a video of the spectacular event at Ostional beach below:

During a typical arribada, as many as 300,000 sea turtles can arrive at the beach over several days.

Once the female turtles have reached a suitable site, the turtles use their back flippers to excavate the nest, leaving behind roughly 100 leathery eggs, each about the size of a ping-pong ball. After the eggs are in the sand, the turtles cover up the nest. For good measure, the turtles rock back and forth, making loud thumping sounds as they “dance” over the nest to compact the sand and camouflage it.

Local efforts to protect turtles have intensified since an infamous incident in 2015 when tourists eager to watch the turtles’ arrival interfered with their nesting.

Today, the rules are much stricter. If visitors want to stand among the sea turtles, they need to be accompanied by a local guide and travel in small groups.

Travelers can get a local guide on the main (and only) road through Ostional at a small green cinderblock building leading toward the beach.

Here are more photos from Sunday’s arribada, via the Association of Local Guides of Ostional: