Just a short ferry ride off the coast of Mexico's Yucatan Peninsula lies the tranquil and tropical island of Isla Mujeres. This tiny strip of sand and swaying palms is famous for its picturesque white-sand beaches, down to earth atmosphere, and fantastic scuba diving - with stunning coral gardens and a massive underwater museum.
But, the true attraction here lies slightly further afield. Each year, the shallow waters around the lesser-known islands of Holbox and Contoy host an incredible gathering of whale sharks. These gentle oceanic giants migrate through the region between March and September in search of their favourite meal - plankton.
And that’s not all. During July and August, off the coast of Cancun, another incredible aggregation takes place. Known as the ‘Afuera’, this gathering of whale sharks is tied to the local spawning of tuna, and arguably, is the biggest whale shark congregation in the world.
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Swimming with whale sharks in Holbox
Holbox whale shark tours from Isla Mujeres offer visitors a once in a lifetime shot at getting up close and personal with the biggest fish in the sea. And, unlike other places in the world, these interactions are 100% natural, with no human intervention to draw the sharks in. This allows visitors to observe these giant filter feeders' wild and natural behaviour as they calmly cruise in the shallows.
Strict protections put in place around Holbox and Contoy are another reason whale shark snorkelling from Isla Mujeres is so unique, limiting the number of guests per day and the size of snorkelling groups. This helps to avoid mob scenes and crowded snorkelling sites that can overwhelm both sharks and visitors alike.
Because the sharks gather in the shallows to feed, the congregations can be easily reached from shore, making these some of the most accessible interactions on planet earth. Plus, the whale sharks tend to cruise close to the surface with their mouths open, collecting plankton as they swim. This makes for the ultimate photo opportunity, with plenty of light to capture the perfect shot! And, with just a handful of guests in the water at a time, your chances of one-on-one interactions are excellent.
Isla Mujeres whale sharks
This second aggregation of whale sharks takes place just outside the Isla Mujeres, Holbox, and Contoy region - hence the name ‘Afuera’, meaning outside in Spanish. This is a vastly larger gathering of sharks, potentially the largest on the planet. Under the cover of darkness during July and August, thousands of little tunny tuna release their eggs here, and as the sun rises, the sharks descend upon the site to vacuum them up. Unfortunately, fish spawns are harder to predict than plankton blooms, meaning this epic congregation is far less structured than the one closer to shore.
Sadly, because this event was discovered later and takes place outside of the protected marine area, few environmental protections have been put in place. This can lead to high visitor numbers and crowded surface conditions during some holidays. And, with many boats, including shipping vessels, permitted to pass through during this aggregation, it is not uncommon to see whale sharks bearing deep wounds left behind by propeller strikes.
While increased protection is paramount here, this is still a once in a lifetime opportunity to swim alongside the biggest fish in the sea. Dozens, if not hundreds of sharks might be spotted during a single tour, and some operators offer multi-day shore-based expeditions to help whale shark fanatics score the highest number of encounters possible.
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Why do whale sharks gather here?
The seasonal population of whale sharks in Mexico’s Yucatan Peninsula migrates into the region in search for their favourite food. Whale sharks are filter feeders, similar to baleen whales, and prefer to dine on tiny organisms that they strain from the seawater. And, they sometimes swim great distances in search of their next meal, following ocean currents as they carry the sea's bounty of plankton from one place to the next.
Several factors contribute to the abundance of nutrition in these waters. This meeting point between the Gulf of Mexico and the Caribbean Sea is fuelled by powerful currents, that ultimately fuel the Gulf Stream. This is one of the planet's strongest flows of water, bringing nutrient-rich upwellings close to the surface and drawing plankton filled water in from the open ocean. Whale sharks also gather further offshore, following seasonal spawning events of tuna and other pelagic fish. Their released eggs are a nutritious and easy to eat delight for the sharks, supplementing their standard diet of plankton and krill.
Whale shark season on Holbox and Contoy has official start and end dates that vary by the year. And, any tour operating outside of them is illegal. This allows the sharks to feed undisturbed, free from human interaction for a portion of their migratory season, which runs from May through July. Off the northeast coast of Isla Mujeres, whale shark season occurs around July and August. The whale sharks then migrate on, though scientists are still hard at work unlocking the secrets of why they leave and where they go.
What to expect
Whale shark tours in Isla Mujeres operate as full or half day excursions, with a normal trip time of around six hours. You can expect water, snacks, soft drinks, and possibly lunch provided for your day at sea, and most vessels offer cushioned seating, shade, and bathrooms onboard.
Snorkelling equipment and life jackets will likely be provided as a part of your tour, but you may want to bring some additional gear along. Exposure protection, including hats, sunscreen, and rash guards or skin suits, can help protect you from the sun and stinging organisms in the water, helping to ensure a fun day at sea. You might also want to bring a waterproof camera, dry change of clothes, towels, and anything else you'll need during the boat ride back to shore.
If you’re based outside of the main towns of Isla Mujeres, Cancun, Cozumel, or Playa del Carmen, you can expect a significantly longer day. But, no matter how short the boat ride, it's a good idea to pack for seasickness. Spending a lot of time in a rocking boat is an easy way to wind up feeling unwell if you aren't prepared - and even guests who aren't prone to seasickness could feel a bit of nausea during extended day trips.
Once your boat has spotted a shark, two guests at a time will be allowed to enter the water. You'll be allowed to swim and snorkel alongside the shark, capturing flash-free photos and videos. Then, you'll reboard your group's boat and let the next buddy team take their turn.
Powerful protection for whale sharks
Unlike other parts of the planet where whale sharks are considered little more than a money-making attraction, the whale sharks of Holbox and contoy enjoy strict environmental protection. In fact, the Mexican government is adding new strategies for conservation all the time, including a major update to regulations, released in 2019.
In open water, motorised boats must remain 30 metres from the sharks. This includes watercraft of all kinds, not just boats designated for whale shark snorkelling. And, boats hoping to conduct whale shark tours must first pass rigorous inspection and certification via the Secretaría de Medio Ambiente y Recursos Naturales - known locally as SEMARNAT. This includes putting propeller covers in place, designed to reduce the number of injuries to whale sharks in the region. A certified guide must lead all tours, with no more than ten visitors per boat, and a maximum of two swimmers per shark at any time. Flash photography is prohibited, touching is strictly forbidden, and when possible, snorkelers are asked to stay a minimum of six feet from the animal.
The government has also set a cap on the number of visitors permitted to swim with the sharks each year at 80,000. And, the tour operators’ whale shark season in Holbox and Contoy is limited to just a few months, allowing these gentle ocean giants to feed undisturbed during other parts of the year.
Wait, there’s more! Sailfish season in Isla Mujeres
Thankfully, the excitement isn't over when the Holbox and Isla Mujeres whale shark seasons end. The powerful Gulf Stream current continues pumping plankton-rich water into the region all year round.
Plankton, krill, and recently released eggs from spawning events are all major attractants for small baitfish. And, anywhere that small fish go, bigger, hungry fish are sure to follow. Around Isla Mujeres, the number one pelagic predator that snorkellers hope to spot is the sailfish. This incredible animal can top out at speeds of over 100 kilometres per hour as it darts in and out of tightly packed shoals of sardines and other small fish, known as bait balls.
Sailfish can instantly change their colours, using skin cells known as melanophores, controlled by their nervous system. This can confuse or startle prey, making it easier to strike. The sailfish can also lower its dorsal fin for faster and more streamlined swimming and raise it during an attack - making its movements harder for the baitfish to predict.
Lucky groups of divers might get the chance to watch these high-speed hunters darting in and out of bait balls, flashing their colours and flying their sails high. As the hunt intensifies, other predators may join in the feeding frenzy, picking off lone fish and cutting straight through the school until all that remains are thousands of glittering scales sinking slowly toward the seafloor. Flash photography is permitted during these tours, but you're better off using an action camera to capture these fast-paced pursuits!
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