Massive Amounts of Jellyfish on Ocean Beach

We are under invasion. By jellyfish.

On Saturday morning, beachgoers were surprised to observe a tremendous concentration of what appear to be moon jellyfish densely packed along the sands of Ocean Beach. The jellyfish, packed in about a 20-foot wide swath, can be most predominantly seen between Pacheco and Lawton Streets.

There is no speculation as to what is behind this, other than just strange coincidence. They probably washed in last night during the high tide.

This detailed picture indicates that the jellyfish are likely moon jellyfish, which are fairly common sights at Ocean Beach. But never in this high of density.

“I’ve lived here 15 years, and I’ve never seen anything like this,” observed a beachgoer. “I’m calling my biologist friend.”

As this picture shows, the diameter of the jellyfish is about the size of a human foot.

UPDATE at 3:16pm.

George Durgerian of the GGNRA was equally surprised by the appearance of the jellyfish, and as of now, “no one is really certain why they are here. There may be some biological implication, but we don’t know about it.”

Durgerian did mention that while this is strange, it is not without precedent. In 2004, tens of thousands of by-the-wind sailors, a type of blue jellyfish about the size of a sand-dollar, washed ashore at Ocean Beach. Their appearance was never fully explained, which may ultimately be the case for this most recent appearance.

The jellyfish pose no harm whatsoever, beyond potentially posing as an inconvenience to beachgoers.

Tagged as:


  1. Makes me nervous! I’m thinking Fukushima?

  2. i see this nightmare every night on summer

  3. I guess the next things we’ll see is a school of beached peanut butter fish.

  4. this is the jeelyfish in the ocean phenomena the little jellybobs are just ahead of the times getting ready for the ocean rising they were just too early goes to show the early bird sometimes flops dead.

  5. these jellyfish have relatively longer lifespans, so its not really a bloom event like which occurrs with phytoplankton or vallella-vallela (sp?). also, they are highlye effected by wind and currents, so my guess is there was some unique current/tide/wind combination along with high biological productivity that caused a density to form and washed on shore. normal.

  6. Jelly fish are just barely mobile on their own, so tides generally predominate where they go. I’ve seen this before with moon jellies down near half moon bay, maybe 3-4 years ago and once with by-the-wind-sailor jellies at Point Reyes McClure Beach, so I wouldn’t say this is profoundly unusual.

    I wonder how much of the novelty of this event is because of communication of the event due to new uses in technology as opposed to this being a rare event.

  7. My intuition tells me that thousands of jelly fish
    came ashore searching for peanut butter fish,
    they’d combine for a tasty treat because of the
    Sand Which Is there…

  8. It was much larger of a swath too, Judah through Rivera streets…..

  9. Some more photos here: I sure hope they figure out why this happened – seems so odd.

  10. Can’t jelly fish sting? I was always afraid of them as a little kid.

  11. Hey I guess this isn’t about global warming. No biggie.

  12. That’s sad, really,really sad. Finding out the cause would certainly be a step in the right direction

  13. By removing the large(r) , more complex predators (seaturtles amongst others) of jellyfish out of the evolution chain, primitive life has fair play.
    Aren’t you interested which primitive life will take over on land?

  14. Are the jellyfish considered dead if they are on the beach? Or are they still alive, waiting for the tide to come back in and take them out to sea? If not, does someone have to clean them off of the beach? It is my understanding that jellyfish have quite a dangerous stinger. I got stung by a jellyfish once and wow did it ever hurt and left a welt. Maybe a different type of jellyfish though.

  15. Tons of jellyfish in the SF Bay earlier this summer.

  16. I wouldn’t refer to it as an ‘invasion’. This seems more catastrophic. How sad. Definitely not normal and I think we should be investigating the reason for this having happened. Jellyfish are a hug part of the ecosystem of the ocean. What could have caused so many to have died. I’m not a oceanographer but I am a lover of the ocean having grown up near it most my life. This saddens me.

  17. I like how our 1st hypothesis is–is it caused by pollution? We should/can test for that but, hey–why not ask a marine biologist and not be terribly alarmist? Tides and migration aren’t caused by pollution, as far as I know.

  18. i swim in the bay and a year or so ago we had a big infestation of the same jellyfish in the aquatic park cove…very odd but kind of eerily cool at the same time…swimming through and randomly touching them, running into them with a yuck and groan…

    very nice pictures. thanks.

  19. I’ve seen this at McNear’s Beach…. two years ago in July it was completely covered in jelly fish. When I was young (about 20 years ago) Ocean Beach used to be covered in Sand Dollars.

  20. Yes, call of your biologist friends~ Ask them why we have been invaded by jellyfish…this is very odd. Not normal at all..Is it? ….I’ve lived here for almost 20 years and I’ve never seen such a thing…What’s happening? Is our ecosystem in trouble…Is it caused by pollution?


  1. Tweets that mention Massive Amounts of Jellyfish on Ocean Beach | The Ocean Beach Bulletin --
  2. Watch your step! Jellyfish take over Ocean Beach | Richmond District Blog of San Francisco (
  3. Ocean Beach Jellyfish Photos | KQED News Fix
  4. New Jellyfish Culture « Outie Sun
  5. Jellyfish at Ocean Beach deemed a "regular event" by local expert | The Ocean Beach Bulletin
  6. Best. Weekend. Ever. | Sunset Local
  7. Case of the Mornings | San Francisco, For the Win
  8. "Bleak" Outer Sunset in New York Times photo essay | The Ocean Beach Bulletin
  9. Ocean Beach Bulletin | BLOGSPOT TEMPLATES
  10. High surf washes jellyfish ashore at Ocean Beach | The Ocean Beach Bulletin
  11. What are those blue, tentacled creatures on Ocean Beach? | The Ocean Beach Bulletin

Leave a Response

Please note: comment moderation is enabled and may delay your comment. There is no need to resubmit your comment.