"Warm Spots" while swimming in the ocean?

So… what causes a thermocline, and why hot and cold water don`t mix?
I´m througly puzzled. :stuck_out_tongue:

Layers of different temperatures occur frequently in water and in air and I am not so sure why anyone would find it surprising.

Ride a motorcyle in the summer and you can feel very significant temperature changes just in a small valley where the road drops by a few tens of feet.

(damn hamsters)

For the ultimate in warm and cold water mixing in your swimming water, try the Blue Lagoon in Port Antonio, Jamaica.

It’s a freshwater spring right near the beach in which cold springwater and warm seawater constantly mix in a deep Blue Lagoon.

Supposedly Jacque Cousteau couldn’t reach the bottom with conventional SCUBA, it’s over 200 feet deep, and Tom Cruise filmed parts of Cocktail there.

Neat little swirlies and currents abound as the warm saltwater and cold freshwater mix all around you. Swim down ten feet and the temperature drops 20 degrees.

I guess water with different characteristics (be it temperature, salinity, whatever) just doesn’t mix as easily as most would suspect. An excellent example of this is the “Meeting of the Waters” near Manaus in Brazil, where the black acidic water of the Rio Negro meets the silty brown water of the Rio Solimões, to form the Amazon. The waters don’t mix for miles downstream and a sharp division can be seen. There are some nice pictures of the phenomenon here, and here.

The following site has this to say:

It wouldn’t surprise me if ocean water shows similiar behaviour when it comes to mixing. So, it seems Thaumaturge’s
answer is the simplest and correct one.

By the way, I have experienced the same thing swimming on the beaches of the Outer Banks, as well as the frigid waters of the North Sea.

IIRC from my diving days, the density of water of differing temperatures is different, and that goes to explain at least partly why the differeing temperature waters will not mix.