Best Time to Dive from Tamarindo, Costa Rica (Catalina Islands & Bat Islands)

There’s a lot of misinformation online about the best time to dive in Northern Costa Rica. Many sites claim the “high season” from December to April is ideal, but the reality is the opposite.

The rainy season, from May to November, is actually the best time to dive.

Closer to February → colder water (down to 16 °C / 61°F), stronger winds, bigger waves, less visibility.

Closer to August → warmer water (up to 30 °C / 86°F), calmer seas, clearer dives.

And for marine life:

Manta rays can appear any time of year, with a slight statistical bump in February (but not a guarantee).

Bull sharks are only at Bat Islands from May through late September, with July and August as the peak months.

Diving Conditions Throughout the Year

Diving here is possible every month, but conditions feel very different depending on when you come:

February (and nearby months): colder water, strong Papagayo winds, surface chop, and lower visibility.

August (and nearby months): warm water, calm seas, great visibility; the kind of diving you picture in a National Geographic video.

October: conditions underwater can still be excellent, but heavy rains make the days less attractive. We usually close operations.

Bull Sharks at Bat Islands

If you want bull sharks, you need to come in the rainy season.

• Season runs June to late September.

• July and August are peak.

• In October, although sharks may still be around, we are closed.
  

👉 For more details, check out our full [Bull Shark Diving at Bat Islands] article.

Manta Rays at Catalina Islands

Manta rays can appear any time of year at Catalina Islands.

• February sometimes brings a few more, but it’s not reliable.

• We’ve seen mantas in almost every month, often when conditions look perfect, sometimes when they don’t.
  

👉 For the full story, see our [Manta Rays at Catalina Islands] article.

Marine Life All Year

What doesn't change much is the amount of life: reef sharks, rays, turtles, schools of jacks, moray eels, and much more. The difference between months is not really about the animals; it’s about how comfortable and enjoyable the dives feel.

Quick Takeaway

• Rainy season = best time to dive.

• Closer to February = rougher conditions.

• Closer to August = smoother, warmer, clearer diving.

• Bull sharks: May–Sept (peak July–Aug).

• Mantas: all year, February sometimes more, but not a rule.

References & Further Reading

• NOAA – Papagayo wind and seasonal upwelling

• Instituto Meteorológico Nacional (IMN) – climate bulletins

• X-Ray Mag – manta ray aggregations at Catalina Islands

• Revista de Biología Tropical – bull shark telemetry at Bat Islands

  
  

A Note from Tamadive

We are a dive center and professional instructors, but we are not scientists or doctors. Everything we share in these articles comes from our daily experience guiding and teaching dives in Northern Costa Rica.

These posts are meant as a reference, not strict rules. Nature doesn’t follow calendars perfectly, and every dive can bring surprises.

If you have different experiences or opinions, we’d love to hear them; send us a message or leave a comment. And if new information comes up, we’ll be the first to update, correct, or extend our articles. Diving is about learning every day, and we’re happy to share that journey with you.