Why is the Caribbean Sea so blue?

Knock-your-socks-off turquoise!

It’s a knock-your-socks-off turquoise.  An eye-popping azure.  A multitude of shades and hues.  

The first time you see the Caribbean Sea, it usually causes a stunned, jaw-dropping reaction. ‘Oh, my god, that’s beautiful.’

Youngsters enjoying the beach near our casa

So, why is the Caribbean Sea so blue?  We’re not trained scientists, just observers, and we read a lot, and this is our version of the reason. 

The colour of water is controlled by a combination of factors – depth, the floor of the sea, suspended particles (soil and pollution) and plankton. Plankton are those tasty little organisms that are the base of the food chain for the big, hungry ocean creatures. 

1987 north of Puerto Vallarta

Depth – well, generally the deeper the water, the darker the colour due to less reflected light.  

However, in our opinion, the deep water of the Caribbean is a brighter sapphire blue when compared to the light jade green of the Gulf of Mexico in the north, or the deep cobalt blue of the Pacific Ocean on the west coast of Mexico. So what else is going on here?

Sand made of coral and seashells reflects the light 

Well, another big influence for determining water colour is what is on the floor of the ocean. Pale pink or bright white sand made from coral bits and degraded sea shells – mixed in with a few bits of lost pirate treasure - reflects light better than the fine, darker sand found in the cooler waters to the north.  

Then, as we mentioned, the amount of plankton and other particles suspended in the water contributes to the colour.  Phytoplankton, for example, harbours chlorophyll that absorbs red and blue light and reflects green. The more plankton, the greener the water. The Gulf of Mexico also has a high concentration of river silt and fertiliser nutrients, added daily by the rivers draining into the Mississippi River basin. All those bits contribute to the pale green colour.

Isla Holbox in the Gulf of Mexico

Even just a few miles north of Isla Mujeres, you will see a dramatic visual difference between the Gulf of Mexico and the Caribbean Sea. The Gulf of Mexico water surrounding Isla Holbox is light green and filled with plankton and nutrients. The Caribbean Sea water is turquoise and has less plankton. The colourful ocean critters that live in our area have apparently adapted to surviving in an environment low on nutrients.   

View of the Caribbean Sea from Isla 33 condos 

Whatever the reason, the Caribbean Sea is just outright gorgeous. The clarity of the water makes it a diving and snorkelling paradise.  

Or if you prefer a more sedentary form of exercise, hanging out by the water’s edge is a totally relaxing way to spend the day. Staring at the colour, listening to the gentle ‘shush’ of the waves, or immersing in the warm salt liquid.   

Heaven on earth.

Lynda, Lawrie, Sparky, and Thomas the Cat

Hanging out in paradise

Isla Mujeres Mystery series

Or

Death in the Vineyards