A Big Fish Expeditions Trip Report
An unforgettable whale shark adventure
This year’s Whale Shark Expedition in Isla Mujeres was nothing short of spectacular. Each day on the water brought us face-to-face with dozens of whale sharks, the largest fish in the sea, along with surprise encounters like graceful manta rays. We snorkeled mere feet away from these gentle giants in calm, clear Caribbean waters, witnessing behaviors that few get to see. Our group was thrilled by the experience, and we’re already planning to return next year (July 28–August 2) during the peak of the season near the full moon for the best chances of even more action.
Giants of the open ocean – whale shark facts
To appreciate this trip, it helps to know a bit about whale sharks. Whale sharks (Rhincodon typus) hold the record as the world’s largest fish, reaching lengths of 12–18 meters (40–60 feet). Despite their immense size, these spotted behemoths are entirely harmless to people. They are pelagic creatures, roaming the open ocean in tropical waters worldwide. Whale sharks live long lives with estimated lifespans of 80 to 130 years based on growth studies. They also mature late. A male whale shark isn’t fully grown and ready to reproduce until around 25–30 years old, which makes conservation important since they recover slowly.
Whale sharks give birth to live young, and they have one of the highest known pup counts of any shark. In fact, a huge female caught in 1996 was found to be pregnant with about 300 pups, each pup about 40–60 cm long at birth. The species is ovoviviparous, eggs develop and hatch internally, and then the mother gives birth to tiny sharks. We didn’t see any baby whale sharks on our trip (those are rarely encountered), but we did observe mostly large adult females cruising and feeding, with only a few younger sharks in the mix.
It’s awe-inspiring to watch a creature the size of a bus glide past you with gentle ease. Whale sharks have huge gaping mouths up to 1.5 m (5 feet) wide, but they aren’t predators in the typical sense, those mouths act like giant strainers. They filter feed by swimming with mouth open, filtering seawater for tiny plankton, fish eggs, and other minuscule morsels. In fact, whale sharks are often called “gentle giants” because they move slowly and feed on some of the smallest creatures in the ocean.
Feeding grounds of Isla Mujeres
Isla Mujeres, Mexico sits near one of the world’s most important whale shark feeding areas. Every summer in July and August, hundreds of whale sharks gather in the Caribbean Sea just north of the Yucatán Peninsula, forming the largest known aggregation of whale sharks on the planet.
Why here, and why at that time? It turns out these waters are rich in food, notably the eggs of spawning bonito (little tunny tuna) that occur in massive amounts during the summer full moons. The local fishermen call the offshore gathering spot “the Afuera” (“outside”), where in 2009 scientists recorded an incredible 420 whale sharks feeding in a roughly 18 km² area during a single aerial survey. The sharks were gorging on dense patches of fish eggs from spawning little tunny, a type of small tuna. This seasonal bounty of fish roe, along with abundant plankton, is what draws the whale sharks here each year.
To protect this natural spectacle, Mexico established the Whale Shark Biosphere Reserve (Reserva de la Biósfera Tiburón Ballena) in 2009. This marine protected area covers about 563 square miles (~1,460 km²) of ocean north of Isla Contoy, Holbox, and Isla Mujeres. It’s a vast sanctuary, roughly the size of a small U.S. state, created specifically to safeguard the whale sharks’ feeding zone and surrounding ecosystem. Within this reserve, regulations limit the number of tour boats and enforce safe interaction guidelines such as no touching the sharks, and no chasing or crowding them, to ensure the whale sharks are not stressed or harmed. We obtained the required permits, which not only protects the animals but also leads to better, more natural encounters for us. It felt good to know we were snorkeling in a protected area where conservation is a priority.
Another fascinating aspect of this region’s ecology is the presence of sargassum (floating seaweed) and other planktonic life. Fortunately for us, this year there wasn’t too much sargassum in the water and the whale sharks had plenty of fish eggs and plankton to feast on.
Calm seas and first encounters
Our first day on the water set a high bar for the rest of the trip. The Caribbean Sea was flat and calm in the morning, the sunlight piercing the blue to give us excellent visibility. Within a short time of reaching the grounds, we had our first whale shark sighting, then another, and another! Suddenly we realized we were surrounded by these giants, with their dorsal fins slicing the surface all around. We were all excited as we donned masks and jumped into the water two at a time.
Nothing can prepare you for the thrill of that first close encounter. We took turns snorkeling alongside the whale sharks, each pair of guests observing sharks as they cruised steadily along.
The highlight of the first day was a surprise manta ray gliding just beneath the surface. Little did we know this was just the first of a few manta sightings during our week. We ended the day with big smiles and a wonderful start. Still, I reminded everyone during our debrief that wildlife is unpredictable and every day is different. We don’t “promise” any specific action because the ocean can always surprise us, for better or worse, on any given day.
Choppy waters but even more action
We woke on our second day to slightly choppier seas. Everyone was eager to get back out there and we could tell it was going to be a busy day. Dozens of other boats from Cancún and Isla Mujeres were zipping about in the morning, as this site is popular with day tours. However, after about an hour or two, the numerous day-tour boats departed the area. By late morning, the crowds thinned out dramatically. I looked around and realized it was just our two Big Fish Expedition boats and maybe a couple of others on the horizon.
The moderate chop didn’t bother the whale sharks at all. In fact, the action was even better than the first day. More manta rays showed up too. This time, at least two mantas were sighted by our guests. One of the mantas was curious and swam within a few meters of our snorkelers. Sometimes you get lucky with a whole cast of marine megafauna sharing the stage.
Everyone got their fill of water time, trading off with patience and respect. We also watched whale shark dorsal fins breach the surface all around. We finished the day tired and excited. Many guests said this was their best wildlife day ever. It’s hard to argue when you’ve swum next to the largest fish in the sea and watched manta rays in their natural habitat.
Whale sharks everywhere
On our third day, a swell rolled in, but it certainly did not deter the whale sharks. By midday, it felt like whale sharks everywhere you looked. With so many giants in the area, every jump was magical. Guests reported unforgettable moments: one snorkeler had a whale shark cruise directly below them, while another guest watched two whale sharks swim side by side as if in tandem.
We also had manta ray encounters again. Scientists recently recognized these Atlantic mantas as a new species distinct from the better-known Pacific mantas. The ones we see here are now called Mobula yarae, the Atlantic manta ray. This species was only formally described in 2023, joining the ranks of the giant oceanic manta (Mobula birostris) and reef manta (Mobula alfredi) as the third known manta species. How cool is it that we are swimming with an animal that science only just named?
The Atlantic mantas (Mobula yarae) are very similar in appearance to the giant mantas, but tend to have a mix of features from both giant and reef mantas. Either way, seeing these huge rays (with wingspans up to ~5–6 m) gliding among whale sharks was extraordinary.
Every person on the trip had multiple quality in-water encounters. We even observed a behavior we call bottle feeding where a whale shark assumes a vertical, tail-down position in the water and gulps repeatedly, filtering dense patches of eggs or plankton near the surface.
Final moments on the water
All great expeditions must come to an end, and day four was our last outing. There’s always a bit of apprehension on the final day. You want to soak up every last moment and you know you’ll miss these encounters as soon as you leave. The morning felt a little slower in terms of whale shark activity. We had been so thoroughly spoiled with constant action. But as late morning turned to afternoon, the whale sharks showed up.
In the final hour of the day, the ocean gifted us a magical closing scene. A group of whale sharks began feeding in close proximity, essentially an aggregation within the aggregation. At one point, three whale sharks swam together within a few yards of each other, with our snorkelers floating respectfully alongside. Those who still had energy slipped in for one more swim.
Over the course of this last session, everyone got their fill of whale shark encounters. We felt a deep sense of gratitude as we watched the last whale shark disappear into the blue distance. In four days, we had observed everything from the dramatic bottle-feeding behavior to large groups of whale sharks cruising together, to close passes by giant mantas. It was the kind of trip where everyone left with lifelong memories and a newfound appreciation for these animals. We encountered only adult whale sharks, mostly females, which is common for this offshore aggregation. Their immense size and grace left us humbled. And thanks to the plentiful food in the water this week (and minimal surface seaweed), the sharks were active and feeding every day.
We ended the day reluctant to head back to the dock, but utterly satisfied with our adventure. Four days with whale sharks had gone by in a blur. Seeing the largest fish in the world up close in their natural element and sharing their space is extraordinary.
Whale Shark Snorkeling July/August 2026
As we said our goodbyes to Isla Mujeres and its seasonal visitors, one thing was clear: we’ll be back for more. In fact, we have already scheduled next year’s Whale Shark Expedition for July 28–August 2 (timed around the full moon when the tuna spawn should be most plentiful). This slightly earlier timing is aimed at hitting the absolute peak of the whale shark aggregation. Every year is a little different, but based on research and past experience, late July through August around the full moon tends to super-charge the feeding event. We’re optimistic that next year could be our best trip yet!
If you’ve been inspired by this trip report, don’t hesitate to book your spot. Snorkeling alongside whale sharks, the biggest fish in the sea, in a wild setting is an experience you will treasure forever. Our expedition is four full days on the water (plus arrival/departure days), led by expert guides and in compliance with marine park regulations. We keep our tour group small and use permitted boats to ensure everyone gets ample time in the water and the animals remain undisturbed. As a bonus, Isla Mujeres is a charming island to relax on after the day’s excitement, and we often swap stories over dinner each evening.
Ready to join? Mark your calendar for next year’s dates and get in touch with us at reservations@bigfishexpeditions.com to sign up or ask any questions. Whether you’re an avid diver/snorkeler or a nature enthusiast eager to witness one of the ocean’s greatest spectacles, this trip is for you. Come meet the whale sharks of Isla Mujeres, and maybe a manta ray or two, and be part of an expedition you’ll never forget. We can’t wait to share this amazing experience with you next time!
