Diving with whalesharks on Koh Tao

When it comes to diving with whalesharks on Koh Tao, there’s a charming little theory floating around among divers and locals on Koh Tao—a theory that, with all the conviction of an old fisherman’s tale, suggests a curious link between rainfall and whale shark sightings. Now, this theory, while about as scientific as predicting the weather by the ache in your knee, does have a certain anecdotal allure to it, and who doesn’t love a good sea story?

Our Marine Biologists at Big Blue Conservation have floated a few ideas that could make sense.

The first idea is all about plankton, those tiny, floating creatures that are essentially the buffet of the sea. When it rains, you see, all sorts of nutrients wash into the ocean from the land. This nutrient bonanza can trigger plankton blooms—an all-you-can-eat feast for the whale sharks. And so, like diners at an all-u-can-eat buffet, they show up in droves, happily gobbling up all the plankton they can find.

Then there’s the matter of temperature. You might not think a bit of rain could make much difference in the vast ocean, but a good downpour can indeed drop the surface temperature just enough to be noticeable. Some folks reckon this cooling effect might lure whale sharks closer to shore, possibly explaining why we didn’t see hide nor hair—er, fin—of them during the scorching, bone-dry summer we had this year. Whale sharks, it seems, may have been off searching for a cooler corner of the ocean.

Next up, water chemistry. Rain doesn’t just make things wetter; it also changes the water’s salinity and pH levels, especially on the surface. This can cause a little shake-up in the marine world, shifting the distribution of all sorts of sea critters, including those that make up the whale sharks’ lunch menu. So perhaps it’s no wonder these giant fish come gliding up to the surface after a good rain.

And, of course, there’s always the possibility that it’s all just coincidence. Whale shark sightings around Koh Tao do seem to peak during certain months that happen to overlap with the rainy season. This overlap might just be enough to make us humans, ever eager to connect the dots, think there’s more to it than meets the eye.

While these theories provide some delightfully intriguing food for thought, it’s worth remembering that whale sharks are complex creatures with habits that are, frankly, as inscrutable as a cat’s. Still, you can’t help but think there might just be a watery dance between rain and whale sharks, a dance we don’t quite understand but are always eager to witness when diving with whalesharks on Koh Tao.

Want to know more about the marine life that patrol these waters: https://www.bigbluediving.com/koh-tao-marine-life/