Los Cabos Snorkel Marine Life Calendar — Sea Lions, Mantas, Whale Sharks by Month

Why the Sea of Cortez runs on a calendar

The Caribbean is, with apologies, a fairly steady year-round destination. You can snorkel Cancún in February and snorkel it again in August and the reef looks essentially the same. The Sea of Cortez does not work that way. The Gulf of California sits between Baja California and mainland Mexico, and it is fed by seasonal upwellings of cold, nutrient-rich water from the Pacific. That nutrient pulse is what makes the gulf one of the most biodiverse ocean basins on the planet — Cousteau's "aquarium of the world" — and it's also what creates the dramatic seasonal rotation of megafauna.

For snorkelers, the practical translation is this: the wow species you came to see are not all present at the same time. Whale sharks arrive when the plankton blooms in La Paz Bay, roughly October through April. Mobula rays aggregate in the southern gulf when the water warms and currents converge, April through July. Gray whales show up in the lagoons of the Pacific coast December through April for calving. Humpback whales arrive in the bay outside Cabo at the same time. Sea lions stay year-round but their behaviour changes — pups in summer, sub-adult social activity in fall, breeding-bull territoriality in late spring. If you plan your trip without checking the calendar you can easily miss the species you most wanted to see.

The data sources for what follows are CONANP permit records, NOAA sea-surface temperature and chlorophyll data, peer-reviewed research published via IUCN Red List species assessments, and operational log books shared with us by partner snorkel and dive operators in La Paz and Cabo San Lucas.

Month-by-month marine life table

Probability ratings: ★★★ = high probability, expect the encounter; ★★ = moderate, season-active but not guaranteed; ★ = low, possible but lucky; — = out of season.

Whale sharks — La Paz Bay, October to April

The whale shark (Rhincodon typus, listed as Endangered by the IUCN Red List) aggregates in two places in Mexico: Cancún / Isla Mujeres in the Caribbean (Jun–Sep) and La Paz Bay in the Sea of Cortez (Oct–Apr). The La Paz aggregation is much less famous than the Cancún one, but for travellers based in Los Cabos it's the closer option.

La Paz is roughly a 2-hour drive north of Cabo San Lucas. The aggregation forms in the protected El Mogote bay just outside the city, where juvenile whale sharks (typically 4–7 m long) come to feed on the plankton blooms that the seasonal upwelling triggers. The activity is regulated by CONANP: permitted operators only, snorkel only (no scuba), no touching, no flash photography, two-swimmer-per-shark rule, and a fixed daily quota of boats inside the observation zone.

Peak months are Nov–Feb. Water temperature drops to 22–24 °C in those months, so a wetsuit is essential — most adults want at least a 3 mm full or 2 mm + rash guard combo. Trip structure: 6–7 am departure from Cabo, 8–8:30 am arrival in La Paz, 9 am boat boarding, two to four swim attempts with whale sharks between 10 am and 1 pm, lunch, drive back to Cabo, arrive 5–6 pm. Cost in 2026 runs $180–250 USD per person for the day trip including transport.

This is a sit-in-place encounter, not a chase. The boat positions ahead of a feeding shark; you slide off the side; the shark passes; you let it. Etiquette is non-negotiable and the rangers are present. We cover this in detail (with the same logic applied to Cancún's whale shark season) in our whale shark tour etiquette guide and the 2026 Cancún whale shark season piece.

Gray whales — Magdalena Bay, December to April

The gray whale (Eschrichtius robustus, classified Least Concern but with the eastern Pacific population conservation-monitored) makes one of the longest annual migrations of any mammal on Earth — from the Bering Sea to Baja California Sur, roughly 8,000 km each way. The whales arrive in Magdalena Bay and adjacent lagoons in December, calve from January through March, and head north again in April.

Magdalena Bay is on the Pacific coast of Baja California Sur, about a 3-hour drive northwest of Cabo San Lucas. It is not a snorkel encounter (gray whales are not approached in water) but it is one of the most extraordinary marine experiences on the planet: mother whales actively bring their calves to small panga boats and the calves solicit physical contact with people. The "friendly whale" behaviour at Magdalena Bay is documented going back to the 1970s and remains unique among large whale populations.

If you are in Cabo any time December–April and you have not pre-booked Magdalena Bay, do it. It pairs well with a same-week whale shark trip to La Paz and the cape's snorkel sites. The trip is operated under CONANP permits, with strict rules on boat numbers, approach distance and time per encounter.

Humpback whales — Cabo's own bay, December to March

The other whale you see from Cabo San Lucas is the humpback (Megaptera novaeangliae), which migrates to the warm waters off Cabo to breed and calve from late November through March. You don't snorkel with humpbacks (the regulation forbids in-water approach by tourists), but you see them from any snorkel boat trip in that season: breaches, tail slaps, mothers nursing calves, occasional singing audible underwater while you snorkel Pelican Rock.

The humpback season at Cabo runs Dec–early Apr, with peak densities in February. If you book a snorkel trip in those months, the boat will routinely detour for whale sightings on the way to the dive site. Cabo's reputable operators all carry the necessary CONANP observation permits and respect the 60 m minimum approach distance (less for mothers + calves).

Mobula rays — the spring spectacle, April to July

The mobula ray aggregation is the wildest thing that happens in the Sea of Cortez and almost no foreign visitor knows about it. From April through July, when the gulf warms and seasonal currents converge, thousands — sometimes tens of thousands — of mobula rays (mostly Mobula munkiana, the Munk's devil ray) form mass aggregations off the cape and along the East Cape.

What you actually see snorkeling: a black river of rays moving across the surface, with individual rays leaping clear of the water — the famous "flying mobula" behaviour, the function of which is still scientifically debated. Aggregations near the cape are often visible from the surface as dark patches, and operators with experience can position the boat so you slip into the water alongside without disturbing the school.

Mobula munkiana is listed as Vulnerable by the IUCN Red List; the species is a focus of regional conservation work coordinated with CONANP. Snorkel etiquette is similar to whale shark: no touch, no chase, give the school the lead. The encounter is not guaranteed on any specific day — aggregations move — but in May and June around the East Cape, you'd be unlucky to miss them.

Sea lions — year-round, with seasonal personality changes

The California sea lion (Zalophus californianus) colony at Land's End is the single most reliable wildlife encounter in Los Cabos. Numbers fluctuate 100–200 animals seasonally, but the colony is resident year-round. What changes is the personality:

• May–early Jun: bull breeding territoriality is at peak. The colony is loud and the bulls patrol aggressively. Operators reposition the swim entry away from the bull territory; encounters are still good but with extra caution.
• Jun–Aug: pupping season. Mothers nursing pups on the rocks; older pups starting to explore the water. Mothers are protective — distance matters.
• Jul–Oct: juvenile prime time. The pups born in early summer are now confident swimmers and at their most playful with snorkelers. This is the best window for the spiraling, bubble-blowing, mask-bumping encounters that go viral on Instagram.
• Nov–Apr: calmer, mixed-age colony. Fewer pups in water but adult sea lions still curious and approachable. Good water clarity in winter, plus the bonus of humpback whale sightings on the boat ride.

If your priority is sea-lion play, time your trip July through October. The colony is also documented on IUCN conservation lists and the population off Baja is part of NOAA's eastern Pacific stock assessment.

Sea turtles — nesting beaches and water encounters

Los Cabos hosts three sea turtle species: the olive ridley (Lepidochelys olivacea, Vulnerable), the East Pacific green (Chelonia mydas agassizii, Endangered) and occasional leatherback (Dermochelys coriacea, Vulnerable). All three are listed and monitored on the IUCN Red List with continuous data feeds to the State of the World's Sea Turtles network.

Nesting season on Cabo beaches runs Jul–Dec, with olive ridley arrivals concentrated on East Cape and Pacific-side beaches. Several beach hotels coordinate with the local tortugueros (turtle protection group) to host hatching releases — typically Aug–Nov. If you are travelling with kids, ask your hotel; participating in a legitimate release is one of the meaningful things you can do on a Cabo trip.

In-water encounters are most likely Aug–Oct, especially at Chileno Bay and along the East Cape (Cabo Pulmo has the most reliable turtle snorkeling). The species you'll most often see grazing on the algae is the East Pacific green. For comparison with the Caribbean turtle scene — where Akumal and the Riviera Maya are the famous spots — see our Cancún snorkeling guide.

How to plan a trip around the calendar

Three scenarios cover most travellers:

Scenario A — Megafauna grand slam (best months: late January to mid-March)

In this window you can stack: gray whales at Magdalena Bay (1 day), whale sharks at La Paz Bay (1 day), humpback whale watching from Cabo (built into snorkel trips), sea lions at Land's End (any morning), and corridor snorkel at Chileno + Santa María. A 5-day trip lets you hit all of it.

Scenario B — Warm water + mobulas (best months: late May to early July)

Water is 25–27 °C and warming, mobula aggregations are at peak, sea lions are entering pupping season, and corridor sites are calm. No whales, no whale sharks, but the spring marine life is the wildest part of the Cabo year. Plan 3 days at Chileno + Santa María + East Cape mobula boat.

Scenario C — Sea lion play + warm water (best months: August to October)

Peak juvenile sea lion behaviour, water 27–29 °C (no wetsuit needed), reliable turtle sightings, and the start of fall whale shark season at the back end. This is also when Cabo sees its lowest tourist counts, which means cheaper hotels and emptier boats. A 4-day trip covers cape + corridor + a sea-lion-focused boat morning.

For deeper month-by-month context on the diving side (which overlaps significantly with snorkel timing), see our Los Cabos diving — month by month.