Sea Turtle Ecology: What I Learned Studying Turtles in Nusa Penida

A 32cm Juvenile Hawksbill Turtle we documented at Batu Nunggul dive site, Nusa Penida, Indonesia April 15, 2025. Photo by Benjamin Khachaturian. @benkhach Instagram.

If you’ve ever had a sea turtle drift past you underwater (calm, ancient-looking, basically unbothered by gravity), you already know why people get hooked on them. They don’t rush. They don’t posture. They don’t panic. They just move, the way they’ve moved for more than 100 million years… quietly doing their thing while the world above keeps changing.

That’s part of why, while living in Nusa Penida, Indonesia, I completed the Sea Turtle Ecology Program with Conservation Diver. I wanted to understand these animals beyond the quick “wow” moment underwater. You see them for ten seconds on a dive, but you’re witnessing a life that stretches back through deep time (something that has survived extinction events, shifting continents, and oceans that were nothing like the ones we know today).

In a world where coral reefs are under pressure and marine systems are reaching critical points, spending time with an animal whose ancestors swam alongside the giant Archelon (that legendary 17-foot-long sea turtle of the Late Cretaceous) can shift your perspective more than any documentary.

So this article is part education, part reflection, part travel guide, and part “here’s what it actually feels like to learn sea turtle ecology next to the cliffs and currents of Nusa Penida.”

The Basics: What Exactly Is Sea Turtle Ecology?

Sea turtle ecology is essentially the study of:

• How sea turtles interact with their environment

• Their behavior and feeding patterns

• How they migrate

• What habitats they rely on

• And how their survival shapes (and is shaped by) the ecosystems around them

But in practice, it’s much more than that. It’s watching a turtle pick through coral rubble for algae. It’s recognizing scars from boat strikes or fishing gear. It’s understanding why certain bays fill with juveniles while deeper reefs attract adults.

Turtles tell the story of a reef.

If coral is the foundation, turtles are the quiet gardeners and wanderers. Hawksbills shape sponge populations. Green turtles keep algae in check. Leatherbacks control jellyfish blooms across entire basins.

Each species plays a different role, and when one disappears, the reef changes in measurable ways.

Why Nusa Penida Is a Perfect Classroom

Nusa Penida is chaotic in the best way. Strong currents, wild thermoclines, underwater cliffs that fall straight into blue-water nothingness… yet somehow it’s also home to peaceful turtle cleaning stations and protected zones where juveniles feed.

During the Conservation Diver course, we:

• Surveyed known turtle hotspots

• Practiced identification skills

• Studied feeding scars on coral

• Monitored turtle behavior over time

• Discussed threats specific to Penida (plastic, boat traffic, illegal fishing)

It’s one thing to read about turtle ecology. It’s another to kneel in the sand at Crystal Bay, watching a hawksbill circle slowly, choosing between soft corals and tunicates like a picky diner.

The course doesn’t turn you into a scientist overnight, but it makes you pay attention—really pay attention—to what’s happening right in front of you.

And honestly, that alone changes your diving forever.

A Glimpse Into the Past: Archelon, the Giant Sea Turtle

Before I get deeper into Penida and conservation, I have to talk about Archelon.

Because no matter how many sea turtles you see, it’s impossible not to imagine what the ocean once looked like when Archelon swam through it—wider than a king-size bed, cruising ancient seas like some kind of armoured spaceship.

This extinct giant roamed about 70–80 million years ago, with flippers as long as your arms and a body weighing the same as a small car.

It gives you perspective:

Sea turtles aren’t just animals. They’re survivors. They’re pieces of an Earth that existed before humans, before cities, before plastic, before the mess we’re asking them to now tolerate.

Every modern turtle carries a lineage that predates our species by tens of millions of years. That’s what made the course hit harder for me personally—the sense that this isn’t just “marine life.” It’s living history.

What I Learned in the Sea Turtle Ecology Program

A sleepy approx. 73cm Hawksbill documented at Sental dive site in Nusa Penida, Indonesia on April 15, 2025 near the famous, gigantic Galaxea coral colony.

Here are some of the biggest takeaways from the course, presented simply and honestly:

1. Turtle identification is more subtle than I expected

Hawksbills and greens are easy to tell apart… until they aren’t. Younger individuals blur the lines, facial scales vary, and lighting underwater plays tricks. But once you get it, you really get it, and suddenly every dive turns into a mental catalog.

2. Behavioral observation matters more than photos

Anyone can take a picture. But noting:

• swim pattern

• feeding style

• habitat use

• avoidance behavior

• time spent resting

…tells a much richer story.

3. Sea turtles rely heavily on specific habitat patches

Some small coral features I would’ve ignored turned out to be important resting or feeding zones. Losing those patches has a bigger impact than I realized.

4. The threats are local, not just global

When we talk conservation, the big narratives dominate: climate change, ocean warming, acidification. But in Nusa Penida, I saw the smaller, fixable issues:

• Plastic snagging on turtle cleaning stations

• Boats speeding over turtle surfacing areas

• Divers crowding individuals

• Fishing line entanglement

It’s heartbreaking because these are solvable today—not someday.

5. Every turtle has a “personality”

Some approach divers. Others immediately bolt. Some stay put and continue grazing even with ten sets of bubbles overhead (not ideal). Once you observe a few individuals repeatedly, you start noticing patterns—little quirks that remind you these aren’t symbols or icons. They’re just animals living their lives.

Sea Turtle Migration: The Most Mind-Bending Part

Sea turtles navigate the ocean in ways that still baffle science. Some cross entire oceans between feeding grounds and nesting sites, returning to the same beaches where they hatched.

The mechanisms behind that might include:

• Magnetic fields

• Chemical cues

• Celestial navigation

• Current mapping over years

Imagine being a hatchling the size of a cookie, swimming into total blackness, and somehow knowing where to go. That’s what we’re dealing with.

And it all ties back to ecology. Migration shapes how turtles interact with environmental change—and how protected areas can help or fail them.

What You Can Do to Protect Sea Turtles (Beyond the Obvious)

Here’s the practical stuff that actually makes a difference:

1. Don’t crowd them when diving

If a turtle changes direction because of you, you’re too close. Simple rule.

2. Support local conservation groups

Places like Aquatic Alliance and Marine Megafauna Foundation actively protect Penida’s turtles and manta rays.

3. Eat fewer (or zero) reef fish

Fishing pressure harms turtles indirectly by destroying food webs and increasing entanglements.

4. Avoid beachfront lighting during nesting season

This disorients hatchlings across the world.

5. Reduce plastic use

It’s cliché, but I’ve physically removed plastic from turtle grazing zones. It’s real.

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Final Thoughts: Why Sea Turtles Matter More Than We Realize

The more time I spend underwater, the more I feel that sea turtles are the “connective tissue” of tropical marine ecosystems. They’re not apex predators, and they’re not coral architects, but their slow, ancient presence keeps certain ecological gears turning.

Learning sea turtle ecology in Nusa Penida added a layer of meaning to every dive I’ve done since. It made the ocean feel older, more fragile, and somehow more alive.

And honestly? Standing on a boat after a long dive, drying off while wind hits your face, and knowing you’re now part of a community actively trying to protect these animals… that feeling stays with you.

It’s why I’m doing this work. It’s why I’m applying for a master’s program. And it’s why I’ll keep going back into the water—because if an animal line that survived the age of Archelon is now depending on us to make the right choices, then the least we can do is pay attention.

As best I could, I uploaded photos of each individual to Manta Matcher for ID and tracking. Most of them were already documented individuals.

View my basic data sheet from the Sea Turtle Ecology program: https://docs.google.com/spreadsheets/d/1nFuWnz5H14xi7ZVwQJgNpDs9cJLhE46Vdk38hEbWPHU/edit?usp=sharing