Diving in Costa Rica (Cocos) in May

Conditions in May

May marks an interesting transition month for diving in Cocos Island, Costa Rica. While the dry season is winding down, you’re not quite into the full swing of the wet season just yet, offering a unique blend of conditions. Expect air temperatures to hover comfortably between 26°C and 30°C (79°F and 86°F). The sea state generally remains calm, particularly in the early parts of the month, though you might experience a slight increase in choppiness as May progresses and the first rains begin to fall on the mainland and surrounding ocean.

Water temperatures around Cocos Island in May are typically warm, ranging from a comfortable 27°C to 29°C (81°F to 84°F). Visibility, while always subject to currents and plankton blooms, tends to be excellent, often reaching an impressive 20 to 30 meters (65 to 100 feet). However, be prepared for occasional thermoclines, which can drop the temperature by a few degrees and introduce a slight murkiness in certain areas, particularly around deeper pinnacles. These thermoclines, while potentially chilly, are often associated with rich nutrient upwellings that attract larger pelagic species. Currents can be moderate to strong, especially around the major offshore seamounts and cleaning stations, adding to the exhilarating drift diving experience that Cocos is famous for.

What you will see

May in Cocos Island is a phenomenal time for encounters with large pelagics, and that’s precisely what you’re here for, isn't it? The hammerhead sharks, the indisputable stars of the show, are present in impressive numbers. You’ll frequently encounter large schools of scalloped hammerheads congregating around the seamounts and pinnacles, often numbering in the hundreds, as they utilize these underwater formations as cleaning stations. Reef sharks, including white-tip reef sharks and grey reef sharks, are also a common sight, cruising the reefs in abundance. You might also be lucky enough to spot the elusive tiger shark or even a silky shark on the blue side.

Beyond sharks, May is an excellent month for manta ray sightings. Both oceanic mantas and Mobula rays are frequent visitors to the cleaning stations, gracefully gliding over the divers. Keep an eye out for marbled rays too, often spotted resting on sandy patches. Large schools of jacks, tuna, and barracuda are a constant presence, swirling in impressive bait balls, creating a truly immersive experience in a vibrant underwater ecosystem. While Cocos isn't particularly known for macro life, the sheer scale of the pelagic action more than makes up for it. Occasionally, you might spot eagle rays or even a whale shark, though these sightings are less predictable.

Top dive sites this month

For an unforgettable May adventure, you absolutely must explore some of Cocos Island's legendary dive sites. Manuelita Coral Garden is an absolute must-do, particularly for its vibrant coral formations and frequent hammerhead schooling opportunities on the sandy slope. The cleaning stations here are bustling with activity, making it a prime spot to witness nature's drama unfold.

Another top contender is Dirty Rock. This iconic seamount is a magnet for pelagic action, offering incredible hammerhead and manta ray encounters, especially on its deeper ledges. Expect strong currents here, but the rewards are well worth the effort. Finally, don't miss Chatham Bay, known for its sheer walls and impressive schools of jacks and barracuda, often with hammerheads patrolling the deeper waters. These sites consistently deliver during May, promising diverse and thrilling dives for every adventurer.

Practical tips for your trip

Given the comfortable water temperatures of 27°C to 29°C (81°F to 84°F), a 3mm full wetsuit or even a 5mm shorty should be perfectly adequate to keep you warm throughout your dives. While thermoclines can drop the temperature slightly, they are usually localized and brief. This time of year is generally suitable for advanced divers due to the potential for strong currents and the nature of offshore diving. While proficient open water divers with some experience in currents can manage, those new to diving might find the conditions a bit challenging. That said, liveaboards are incredibly well-equipped to guide divers of all levels, and your divemaster will always brief you thoroughly.

Liveaboard availability in May can start to tighten as it’s a popular transition month, so it’s always wise to book your trip well in advance – ideally 6 to 12 months ahead for prime spots. Beyond your standard dive gear, remember to pack reef-safe sunscreen, a wide-brimmed hat, and insect repellent for your time on the liveaboard deck. A good quality underwater camera is an absolute must to capture the incredible pelagic encounters you're guaranteed to have. Be aware that Cocos Island is a remote destination, so satellite communication is the norm, and internet access is often limited or non-existent, allowing you to truly disconnect and immerse yourself in the diving experience.