The Ostional Arribada: One of Costa Rica’s Most Incredible Natural Phenomena
Photo by Turtleland Tours
If you’ve never heard of an arribada before, you’re not alone.
Even many people who visit Costa Rica have no idea that, near Nosara, one of the wildest natural phenomena in the world happens almost every month.
Thousands — sometimes hundreds of thousands — of Olive Ridley sea turtles come ashore at the same time to lay their eggs on the beach.
And somehow, despite decades of research, scientists still don’t fully understand why they do it.
Seeing an arribada in Ostional is one of those experiences that feels hard to explain until you witness it in person. It’s chaotic, peaceful, emotional, overwhelming, and strangely beautiful all at once.
Here’s what the Ostional arribada is actually like, how it works, what to expect from a tour, and why this small beach near Nosara is globally important for sea turtle conservation.
What Is an Arribada?
The word arribada means “arrival” in Spanish.
It refers to a phenomenon where huge numbers of Olive Ridley sea turtles come ashore together over the course of several days to lay their eggs.
Ostional, located about 30 minutes north of Nosara, is one of the most important arribada sites in the world.
And when we say lots of turtles… we mean LOTS.
The first thing that shocks most visitors is the sheer number of turtles.
They seem completely synchronized — all slowly moving toward the same stretch of beach, all focused on the exact same mission.
It honestly feels surreal the first time you see it.
Why Does It Happen?
That’s the crazy part: scientists still don’t fully know.
Arribadas are associated with the last quarter moon, and there are definitely patterns, but the timing is still unpredictable.
Sometimes turtles skip a month.
Sometimes there are two arribadas in one month.
Sometimes activity builds for days and then suddenly slows down.
That unpredictability is part of what makes the experience feel so special.
Nobody can guarantee exactly when the next big arribada will happen.
Is It Worth Planning an Entire Trip Around?
Probably not.
Because timing is unpredictable, we usually recommend thinking of it as an amazing possible bonus experience rather than the single reason for your trip.
That said, September and October tend to have some of the biggest arribadas of the year. The number of turtles during those months can be absolutely crazy.
Even outside the main arribada periods, though, Ostional is still worth visiting. It’s a beautiful black sand beach, and there’s often still turtle activity happening — including solitary nesting turtles or hatchlings making their way to the ocean.
If you’re visiting during rainy season, this is also one of the times of year when the entire area feels especially green and alive. We wrote more about that here: Rainy Season in Nosara: What It’s Actually Like.
What It Actually Feels Like to Witness an Arribada
The moment most people remember is stepping onto the beach for the first time.
Suddenly there are turtles everywhere.
Some are emerging from the ocean.
Some are digging nests.
Some are laying eggs.
Others are slowly making their way back toward the water.
And somehow, despite all the movement, the beach still feels strangely calm.
If you go early in the morning, sunrise during an arribada is unforgettable. Watching the sky slowly brighten while turtles continue crawling across the beach feels almost unreal.
At night, the atmosphere feels completely different — darker, quieter, and more intense.
Either way, it’s one of the most memorable experiences near Nosara.
What Is the Tour Actually Like?
Tours are usually either:
very early morning (around 5 AM)
or shortly after dark (around 6-7 PM)
The experience itself is easy physically. You mostly walk along the beach while your guide explains the turtles’ nesting process and helps you spot activity.
A few practical things to know:
Regular comfortable clothes are fine
Photos are allowed, but flash photography is not
You should expect darkness during night tours and will use red lights to see the turtles
Tours are generally family-friendly as long as everyone can comfortably walk on uneven sand
If you’re visiting Nosara with children, we also put together a full guide to What to Do in Nosara with Kids — including beaches, activities, transportation, and family-friendly tips.
The Egg Harvest: What Visitors Often Misunderstand
One thing that surprises many visitors is learning that limited egg harvesting is legally allowed in Ostional.
At first, this sounds shocking to some tourists — until they understand how the arribada works.
Because so many turtles arrive over several days, many of the earliest nests would actually get destroyed anyway by later turtles digging new nests in the same areas.
The community-managed harvest focuses on those early eggs, and the system has become an important part of local conservation efforts and the local economy.
Your guide will usually explain this process in much more detail during the tour itself.
Hatchlings: A Completely Different Experience
If you miss the main arribada, hatchling tours can also be really special.
About 45 days after eggs are laid, baby turtles begin emerging from the sand and making their way toward the ocean.
The experience feels very different from an arribada.
Instead of massive numbers of adult turtles spread across the beach, hatchlings tend to emerge from concentrated areas. Visitors and locals often help keep an eye out for predators like vultures while the babies make their way to the water.
For families and kids especially, hatchlings can be an incredibly memorable experience.
Our Favorite Turtle Guide Near Nosara
Over the years, we’ve met a lot of guides around Nosara, and for turtle tours we always recommend Fran from Turtleland Tours.
He’s bilingual, incredibly knowledgeable about the arribada and conservation efforts in Ostional, and honestly just a great person to experience it with. His tours feel educational without feeling overly scripted, and he’s been guiding visitors through turtle season for years.
Because arribadas are unpredictable, one of the hardest parts is simply figuring out when there’s real activity happening.
If you’d like help connecting with Fran or figuring out whether there are turtles active during your trip, feel free to send us a message and we’re happy to help.
Final Thoughts
The Ostional arribada is one of those experiences that reminds you how strange and incredible nature can be.
Thousands of turtles all arriving together.
Cycles that scientists still don’t fully understand.
Tiny hatchlings somehow finding the ocean for the first time.
It’s unpredictable and completely unforgettable.
And even after seeing it multiple times, stepping onto the beach during a big arribada still feels surreal.
Planning a Trip to Nosara?
If you’re still organizing your trip, these guides may help: