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Hotels, dive operators, gear, and how to get here are on the Catalina Islands location page.
Overview
A volcanic rock face on the outer Catalina Islands off Guanacaste, dropping from about 12 metres to past 24 along a single sloping wall locals call Shark Alley. Cold nutrient-rich upwellings between November and April pull oceanic manta rays with wingspans over 6 metres, mobula schools of dozens to hundreds, and squadrons of cow-nosed and spotted eagle rays through the cleaning stations on the ridge. White-tip reef sharks rest in the channels at the base, with schooling jacks, snapper and the occasional bull or whitetip in the blue. Strong tidal currents and a sharp thermocline make for serious diving, but it is the most reliable Pacific manta encounter in northern Costa Rica.
Briefing note
Strong tidal currents and surge make this an advanced-only dive — most operators require Advanced Open Water and previous current-diving experience. Oceanic mantas concentrate at the cleaning stations from late November through April, peaking January to March. Big Pacific swells in winter occasionally cancel the boat trip.
What you'll see
8 species curated- seasonalOceanic manta rayPeak: Nov · Dec · Jan · Feb · Mar · Apr
- seasonalMunk's devil rayPeak: Dec · Jan · Feb · Mar · Apr · May
- seasonalCow-nosed rayPeak: Nov · Dec · Jan · Feb · Mar · Apr
- year-roundSpotted eagle ray
- year-roundWhitetip reef shark
- year-roundPacific green turtle
- year-roundBigeye jack
- year-roundKing angelfish
Sightings evidence
1 record on file- medium confidenceOceanic manta ray
- Last confirmed
- Apr 2026
- Recent records
- 45 within 25 km
- Cluster months
- Nov, Dec, Jan, Feb, Mar, Apr
Sources & methodology
How we summarise this
We aggregate confirmed occurrence records from GBIF and OBIS within a fixed radius of each dive site. Occurrence records confirm presence and reveal seasonality clustering, but they DO NOT measure per-dive probability — there is no eligible-effort denominator. We deliberately do not publish a numeric '% chance of sighting' from this data.
Sources
- Global Biodiversity Information Facility — GBIF Secretariat
- Ocean Biodiversity Information System — IOC-UNESCO
- iNaturalist — California Academy of Sciences & National Geographic Society
- IUCN Red List of Threatened Species — International Union for Conservation of Nature
- Manta Trust IDtheManta Database — Manta Trust
- OBIS-SEAMAP — Duke University Marine Geospatial Ecology Lab / OBIS
- WoRMS — World Register of Marine Species — Flanders Marine Institute (VLIZ)
- FishBase — FishBase Consortium
- Atlas of Living Australia — CSIRO / GBIF Australia
- REEF Volunteer Fish Survey — Reef Environmental Education Foundation
Conditions
| Month | Water | Visibility | Current |
|---|---|---|---|
| Jan | 18–22 °C | 10–25 m | strong |
| Feb | 17–21 °C | 10–25 m | strong |
| Mar | 18–23 °C | 15–30 m | strong |
| Apr | 22–26 °C | 15–25 m | moderate |
| May | 25–28 °C | 10–20 m | moderate |
| Jun | 26–29 °C | 8–15 m | moderate |
| Jul | 27–29 °C | 8–15 m | moderate |
| Aug | 27–30 °C | 8–15 m | moderate |
| Sep | 27–30 °C | 8–15 m | moderate |
| Oct | 26–29 °C | 8–18 m | moderate |
| Nov | 24–27 °C | 12–25 m | moderate |
| Dec | 20–24 °C | 12–25 m | strong |
Season calendar
Peak season highlighted · current month outlined
Gear for this site
Beyond the basic kit- Temperate wetsuit — Upwellings in manta season push water below 20°C with sharp thermoclines — a 5mm full suit plus hood is standard from December through March.
- SMB + reel — Drift profiles along the wall regularly end in blue-water ascents; surface marker buoy is required for boat pickup in current.
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