We noticed that you're using an unsupported browser. The TripAdvisor website may not display properly.
We support the following browsers:
Windows: Internet Explorer, Mozilla Firefox, Google Chrome. Mac: Safari.

Red tide?

Which Playas del Coco hotels are on sale?
dd/mm/yyyy dd/mm/yyyy
See hotels
Mukwonago, Wisconsin
1 post
Save Topic
Red tide?

Is it safe to swim when there is a red tide? We are coming down in mid March. Will it still be there?

Level Contributor
3,091 posts
46 reviews
Save Reply
1. Re: Red tide?

I do not expect it to stay for that long.

Personally I do not like to swim in it, but it is not all over the beach.

I saw it in the Nicoya gulf. It occurs when the temperature of the ocean water rises.

I would not worry about this issue.

Costa Rica
Level Contributor
545 posts
9 reviews
Save Reply
2. Re: Red tide?

I don't like to swim in it either and it does come and go. We were sailing yesterday and we can see clearly where the red tide is and where it is not. The currents move it around. It happens rarely and doesn't stay long, hopefully it is all gone by the time you are here! I expect it to be. In fact, the day before yesterday it was gone from Coco Bay, but then came back yesterday. Today is less, but still there.

I saw it as far south as Caldera, near Puntarenas, 3 days ago.

Huntsville, Canada
Level Contributor
368 posts
1 review
Save Reply
3. Re: Red tide?

Flew over the bay San Jose to Tambor 16 Feb and it was very obvious (long strips of red). During the week red tide could be seen in the waves at Tambor and only the odd person was in the water. Flying back to San Jose on the 23rd red tide was completely gone from what I could see.

Costa Rica
Level Contributor
545 posts
9 reviews
Save Reply
4. Re: Red tide?

Just fyi, the red tide has been gone from Coco for a couple/few days now!

Costa rica
Level Contributor
87 posts
52 reviews
Save Reply
5. Re: Red tide?

Bad news .....marea roja ...

still in the Bejuco, San Miguel and Coyote area ....

Very difficult to figure out, what will be the pattern for the next days .... !!!!

Current inshore moves N/W to S/E ... few km offshore runs the other way ....


Costa Rica
Level Contributor
545 posts
9 reviews
Save Reply
6. Re: Red tide?

The Costa Rica Dome and Phytoplankton Treasures

Article taken from; news.co.cr/tourism/…

Select Language​▼

Author’s Note: A lot of the information on this article comes from the Environmental section of the digital news daily El Pais and the National University.

The alleged naming of Costa Rica by Christopher Columbus during one of his final voyages of discovery is often the subject of tongue-in-cheek jests by Ticos who know better. “He had no idea”, goes the saying, particularly when making reference to the amazing blessings that Nature keeps bestowing upon the country. Recent studies into the Thermal Convection Dome and the rich biomass it creates underscore the importance of the Costa Rica Dome to life in the ocean.

The Aqua satellite image from the National Aeronautics and Space Administration that accompanies this article was reviewed by scientists at the National University in Heredia in mid-February, 2012. The dark red aspect of the image shown off our north Pacific coast is not red tide; it rather represents the highest concentration of chlorophyll in the world, up to 60 milligrams per cubic centimeter of sea water. This means that a lot of phytoplankton -unicellular algae that eventually photosynthesizes into plankton- is available for the pleasure of a number of migratory marine species, including crabs, dolphins, marlin, tuna, turtles, whales and more. These species swim and crawl across thousands of kilometers to feast and reproduce off our coast.

The Costa Rica Dome

Marine species that feast off our Pacific coasts can thank the phenomenon created by the Costa Rica Dome for the hundreds of thousands of square kilometers of nourishment available to them. The Alpha of the Dome is located in the depths of the Cocos underwater tectonic valley, which is not only the cause of many earthquakes, but it’s also responsible for a subaquatic cyclonic current that moves in harmonious sync with the air current above sea level. The axis of rotation of the Costa Rica Dome is located way off to the west of the Isla del Coco. The balmy weather and convective energy produced by the dome guarantees a constant process of photosynthesis that is rich in phytoplankton.

In this other satellite image showcased at the Visible Earth gallery of NASA, the inter-tropical convergence zone can be appreciated in the midst of the dome and close to our shores. The deep green areas are extremely rich in phytoplankton, and these are the precise areas where marine biologists have observed deep concentrations of marine life, from fish to algae and from crustaceans to mammals. That image was published in 2001, and taking a look at the image showing the chlorophyll concentration levels, it’s easy to see that the Costa Rica Dome is still thriving.

Benefits of the Costa Rica Dome

The atmospheric and oceanic benefits of the Thermal Convection Dome are evident to the marine species that live and migrate just off our shores. Whales, dolphins, turtles and other migratory species will want to keep coming back to feed and procreate, thus ensuring that the world’s oceans teem with life; which in the end attracts even more wildlife (think about sea birds). For Ticos, it’s a source of deep pride and one more thing to add to their bragging rights of living in a country that is truly blessed by nature. In an article appearing in El Pais, author Guillermo Quiros Alvarez points out that while the Costa Rica Dome is but one of her wonders, not enough awareness is being promoted at the school level. Teachers and Ministry of Education officials reading this, please take note.

For the fishing communities of the Pacific, the Dome -when not affected by atmospheric events by El Nino and La Nina- is a rich source of sustenance. Under international maritime law, the government can only protect a few square kilometers of the ocean in a straight line from the coast, and to this extent there isn’t much danger of overfishing, as long as the phytoplankton levels remain close to our coast.

Whale Watching and Ecotourism

In terms of ecotourism, the benefits are tremendous. It is estimated that whale-watching brings in more than $20 million a year to at least 10 fishing communities, according to marine conservation group MarViva. As long as sustainable and responsible fishing is practiced in the Dome areas, whales will keep coming back. The conservation policies that were enacted around the country in the 1970s are paying off in the 21st century, as it has become easier to spot the gentle giants off our Pacific shores (not far from the Envision Festival).

One organization that wishes to call greater attention to the Costa Rica Dome is the Environmental Protection of the Islands Corridor (EPIC). This initiative is spearheaded by Eduardo Acosta, a former residential developer who is the author of a book about a sea turtle that is besieged by threats to the Costa Rica Dome. The planned EPIC Park will be a nature-themed attraction that will focus on educating visitors about the Dome. The heroine of Eduardo’s book is named Hope, and she also has the potential to educate young students about the Dome.

Whale lovers should also take note that the Costa Rica Coalition for Whales will be holding a special screening of Big Miracle, a new film starring Drew Barrymore about whale conservation efforts in Alaska. The film will be screened at the Terramall theaters at 7:30pm on February 23. Costa Rica will be present at the future International Whaling Commission summit, and Ticos are expected to take a strong stance against commercial whaling around the world, unless it is practiced by native tribes.

Methane Clathrate in the Dome

The ocean floor beneath the Dome is rich in methane chlathrate, a byproduct of the life and death process of the rich biomass closer to the surface. For millions of years, the sediments of the ocean floor off our Pacific coasts have been accumulating millions of metric tons of methane clathrate, also known as fire ice, a compound that is believed to be far more powerful that natural gas in terms of energy production. Oceanographic research vessels bearing flags of industrialized countries have been sailing the oceans past our international maritime demarcation line, taking samples from the depths. The result of the research thus far? Costa Rica is ripe for exploration and prospecting of fire ice, something that could make Ticos richer than the oil-producing nations of the Middle East.

Given Costa Rica’s track record of resisting mineral exploration; to wit: the Crucitas affair and the reluctance of prospecting for rare earth, it is unlikely that we will see initiatives for the exploitation of the Costa Rica Dome. If anything, it is incumbent upon Ticos to protect the Dome and the life it produces.

Montezuma, Costa...
Level Contributor
538 posts
8 reviews
Save Reply
7. Re: Red tide?

By mid-March, we all expect it to be well gone.

You should not swim in it, it is heavy in bacteria..

There are also lots of freshwater river ponds for dipping in

Stittsville, Ontario
Level Contributor
2 posts
209 reviews
Save Reply
8. Re: Red tide?

Just FYI, we have just arrived in Playa del Coco (March 28th) and the Red Tide is still very present here in Coco, as well as nearby Ocotal. The beach in Ocotal in particular is littered with tons of dead puffer fish, and noticeably red water at the shoreline. It is very sad to see. However, we are told by fellow tourists and locals that it is localized to here, and beaches such as Tamarindo and others are fine. . . . .We have been advised not to swim here while it is present.

Costa Rica
Level Contributor
545 posts
9 reviews
Save Reply
9. Re: Red tide?

This is the longest stretch of Algal Bloom I have seen since I have been here. And I said before, I saw it all the way down as far south as Caldera. I did not see it in Jaco and south of there when I was down there earlier this month. This is normal though and it is caused by the strong Papagayo Winds that typically blow between Dec and April.

The "red tide" or Algal Bloom is clearly visible when you put on your polarized sunglasses. You can clearly see the red and blue water. The water can be clear blue in the morning and by afternoon full of red water. It changes by the hour, moving with the currents.

Read about it more;


"Red tides

A red tide

Red tide is a term often used to describe HABs in marine coastal areas,[13] as the dinoflagellate species involved in HABs are often red or brown, and tint the sea water to a reddish color. The more correct and preferred term in use is harmful algal bloom, because:

these blooms are not associated with tides

not all algal blooms cause reddish discoloration of water

not all algal blooms are harmful, even those involving red discolouration[14]"



......when the Papagayo blows, the sea follows. The wind mixes the normally warm surface waters with colder, nutrient-rich water that lies beneath the shallow thermocline near the coast. Algal blooms propagate in the path of the Papagayo, fueled by the banquet of nutrients. An entire food chain, ascending to the majestic marlin and sailfish sought by sport fishermen, depends on the episodic Tehuano and Papagayo events."

It is very sad seeing dead puffer fish, eels, rays, jellyfish, etc. You see more puffer fish than anything because they float to shore.

What else is really, really really really sad is finding a place with great visibility for going snorkeling with clients and when you are out you witness another tourist with a spear-gun shooting anything and everything they can out in front of the Four Seasons. We tried to find out who they were but there was no other boat around. (and we were snorkeling with clients.) It was the strangest thing ever. Why spear King Angle Fish all kinds of other fish, that are small and young and not edible??? Anyone have any idea what to do about that??? They were 2 guys, spearing everything and they had a large bag filled with dead baby fish. Why??

Sorry to get off subject but I just don't know who to tell about that or what can possibly be done. Can we start a fight with people spearfishing while we're on a snorkeling tour with clients? If I personally were in the water and witnessed it, I would not have been able to remain quiet. But our snorkel guide witnessed it and was very upset when telling me about it later that day. That was yesterday or the day before......yeah, it was yesterday.

Brooklyn, New York
12 posts
Save Reply
10. Re: Red tide?

I am traveling to Dominical in 2 weeks. Do you think it will affect that area?

Thanks for any help!!