Bull Shark Diving at Bat Islands (Murciélago), Costa Rica
- Franko Merlo
- Dec 5, 2025
- 7 min read
Diving with Bull Sharks: What the First Descent Really Feels Like
The first descent at Big Scare is something most divers never forget.
We drop in over a rocky bottom that slowly slopes down into the blue. At around 12 meters / 40 feet, we settle in and wait.
You can feel it immediately. A mix of excitement, tension, and curiosity. Some divers are nervous, others are eager, most are somewhere in between. Everyone is watching the water, scanning the blue, waiting.
Then you see the first one.
That moment hits hard. A sudden realization. It is real. It is here. The size is impressive. If a bull shark comes closer, the adrenaline spikes. But almost as quickly, something else happens. You begin to notice how calm the situation actually is.
They approach. They observe. And then they move away. They keep their distance. Many divers are surprised by this. In fact, to get good sightings, you often have to actively look for them, rather than wait for them to come to you.
Let's mention it just in case : DO NOT CHASE BULL SHARKS
That is when fear fades and respect takes its place.
For many divers, this is the moment when their perception of sharks changes completely. What looked intimidating from the surface becomes controlled, predictable, and surprisingly peaceful underwater.
As instructors, we see this transformation every season. And honestly, if there is one thing we sometimes wish for, it is to forget these dives just to feel that first encounter again. Over time, professionals normalize wonders that should never feel ordinary.
That is why diving with bull sharks at Bat Islands is not just about seeing a shark. It is about experiencing that transition from anticipation, to adrenaline, to understanding, all in a single dive.
What the Bat Islands Dive Is Really Like
Bat Islands are located inside Santa Rosa National Park and are famous for a specific dive site known as Big Scare (guess why).
A typical Bat Islands trip includes three dives.
The first two dives are deep dives, usually around 30 meters / 100 feet, focused on observing bull sharks cruising calmly through open water. These encounters are natural, controlled, and never baited.
The third dive is shallower and very different. It often features large schools of jacks and snappers, eagle rays, turtles, and occasionally manta rays.
Dolphins are sometimes seen during the boat ride.
Tiger sharks are not part of this dive experience but if we can get VERY lucky : whalesharks.
Bull Shark Behavior: Understanding the Real Risk
Bull sharks are often described as one of the more dangerous shark species, and this reputation has some basis in reality. Out of more than 500 shark species, only a small number are involved in the majority of serious unprovoked incidents, and bull sharks are among them.
This is not because they actively target humans as prey, but because of where and how they usually live.
Most documented incidents occur in rivers, estuaries, and murky coastal waters, where sharks rely heavily on electrosensory cues rather than vision. In these environments, defensive or mistaken bites are more likely.
At Bat Islands, the context is completely different. Dives take place in open ocean conditions, in saltwater, at depth, and with predictable movement patterns. Here, bull sharks are not hunting in confined or low visibility spaces. They are cruising calmly through open water.
Humans are not part of their natural diet, and when dives are conducted correctly and protocols are respected, encounters are stable, controlled, and remarkably calm.
When Is the Best Time to Dive with Bull Sharks at Bat Islands
Bull sharks are present from May to late September, with July and August being peak months.
Although sharks may remain slightly longer, we do not operate Bat Islands trips in October due to weather and logistics.
If bull sharks are your main goal, the rainy season is the correct time to plan your trip.
Bull sharks are present in the North Pacific of Costa Rica year round, but that does not mean they use every dive site in the same way throughout the year.
What changes is how consistently they use Bat Islands (Isla Murciélago).
Based on long-term observations and scientific acoustic monitoring, Bat Islands function as a seasonal aggregation site, not a permanent habitat. From May to September, and especially during July and August, bull sharks are detected far more frequently at this specific location.
During these peak months, the same tagged individuals return repeatedly, sometimes over consecutive days, making encounters not just possible, but reliable.Outside of this period, bull sharks may still pass through the broader region, but their use of Bat Islands becomes sporadic and unpredictable.
This is why bull shark diving is considered seasonal in practice, even though the species itself does not disappear from the area.
👉 If you want to understand how scientists measure this presence, what acoustic detections really mean, and how to correctly read the seasonal graph, read our in-depth article on How Bull Shark Presence Is Measured at Bat Islands.
👉 To learn why July and August stand out, and what environmental factors influence bull shark residency, continue with our detailed breakdown in Why Bull Sharks Aggregate at Bat Islands.
Certification Requirements for Deep Diving (30 meters / 100 feet)
Due to depth and conditions, Advanced Diver certification is required.
Open Water divers may complete only the Deep Adventure Dive portion of the SSI Advanced Adventurer course, for an additional cost. This allows us to safely and 'legally' take them to the required depth under direct professional supervision.
This does not certify the diver as Advanced unless the full course is completed.
FAQs
Are bull sharks aggressive toward divers
Bull sharks are powerful animals, but humans are not part of their natural diet. In open ocean environments like Bat Islands, encounters are calm when proper protocols are followed.
Can Open Water divers join bull shark dives
Yes but Not by default. SSI standards require additional training due to depth.
Are bull shark encounters guaranteed
No. All wildlife encounters are natural and unpredictable.
References & Further Reading
A Note from Tamadive
We are a dive center and professional instructors, but we are not scientists or doctors. Everything we share in these articles comes from our daily experience guiding and teaching dives in Northern Costa Rica.
These posts are meant as a reference, not strict rules. Nature doesn’t follow calendars perfectly, and every dive can bring surprises.
If you have different experiences or opinions, we’d love to hear them—send us a message or leave a comment. And if new information comes up, we’ll be the first to update, correct, or extend our articles. Diving is about learning every day, and we’re happy to share that journey with you. Bull Sharks in Costa Rica: Clearing the Misinformation
There is a lot of misinformation online about bull shark diving in Costa Rica. Many websites claim that bull sharks can be seen year-round at Bat Islands. From our experience diving this site consistently, this is simply not true.
At Bat Islands, bull sharks are seasonal. They appear during the rainy season, when conditions, water temperature, and food availability align. Choosing the right time of year is essential, and this is why understanding local conditions matters. We explain seasonal patterns in detail in our article about the Best Time to Dive from Tamarindo.
What the Bat Islands Dive Is Really Like
Bat Islands are located inside Santa Rosa National Park and are famous for a specific dive site known as Big Scare.
A typical Bat Islands trip (with us) includes three dives.
The first two dives are deep dives, usually around 30 meters / 100 feet, focused on observing bull sharks cruising calmly in blue water. These encounters are natural, predictable during the season, and never baited.
The third dive is shallower and very different. It often includes large schools of jacks and snappers, eagle rays, turtles, and occasionally manta rays.
Dolphins are sometimes seen during the boat ride.
Tiger sharks are not part of this dive experience!
These dives clearly show why professional guidance is critical underwater, something we explain further in What Recreational Divers Don’t Realize: The Reality of Diving from the Professional’s Side.
When Is Bull Shark Season at Bat Islands?
Bull sharks are present at Bat Islands from May to late September-october.
July and August are consistently the peak months, offering the highest probability of multiple encounters per dive.
Although bull sharks may remain slightly longer, we do not operate Bat Islands trips in November due to weather conditions, logistics, and park access. Outside this window, reliable encounters cannot be expected and navigation can get pretty dangerous.
If bull sharks are your main goal, the rainy season is the only correct time to plan your trip.
Certification Requirements for Bull Shark Diving
Due to depth, currents, and overall conditions, Advanced Diver certification is required for bull shark dives at Bat Islands.
However, many Open Water certified divers ask if there is a way to join.
FAQs
Can Open Water divers join bull shark dives? Not by default. Under SSI standards, Open Water certification alone does not allow diving to the required depth.
Is there an option for Open Water divers? Yes. Open Water divers can complete only the Deep Adventure Dive portion of the SSI Advanced course with us, for an additional cost. This allows us to legally and safely take them to the required depth under direct professional supervision.
Does this certify me as an Advanced Diver? No. Completing only the Deep Adventure Dive does not certify you as an Advanced Diver. Full certification requires completing the entire course.
Why is this required? Because bull shark dives are deep dives. Following training standards ensures safety, control, and a better experience for everyone.
Are bull shark encounters guaranteed? No. All encounters are natural and unpredictable. We never guarantee sightings.
References & Further Reading
A Note from Tamadive
We are a dive center and professional instructors, but we are not scientists or doctors. Everything we share in these articles comes from our daily experience guiding and teaching dives in Northern Costa Rica.
These posts are meant as a reference, not strict rules. Nature doesn’t follow calendars perfectly, and every dive can bring surprises.
If you have different experiences or opinions, we’d love to hear them—send us a message or leave a comment. And if new information comes up, we’ll be the first to update, correct, or extend our articles. Diving is about learning every day, and we’re happy to share that journey with you.
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