Why is the water clear at some beaches but not others?

Question

Why can you not see your feet when you stand in the water of an atlantic beach but you can in a caribean beach?

Answer 1

It is a combination of suspended solids, and the amount of organisms living in the water. Tropical oceans are the equivalent of deserts on land, and have significantly fewer nutrients in the water for phytoplankton to use for food. The other major difference between US Atlantic coast beaches and the Caribbean is the prescence of a thermocline in the Caribbean.

Most Caribbean beaches have very limited sources of suspended solids such as rivers. Many Caribbean beaches also have lower levels of wave action than the Atlantic US coast, so the suspended material will settle out more quickly. After a hurricane in the Caribbean the beaches will be just as muddy looking as any Atlantic coast beach. For the Caribbean, a major source of suspended sediment is actually dust in the air which sometimes travels from as far as Africa. Obviously this source is much smaller than the many rivers carrying sediment to the Atlantic coast of the US.

The rivers that carry suspended solids into the Atlantic US east coast are also major sources of dissolved nutrients. In the Caribbean the primary source of dissolved nutrients is from the decomposition of dead organisms in the water column. When these organisms die in the Caribbean they sink into a lower layer of water created by a temperature difference, called the thermocline. Since this lower water rarely circulates with the upper layer of water, the nutrients in the surface water are extremely limited. The result is very little phytoplankton in the upper water and clear beach water. On the US east coast of the Atlantic this type of thermocline does not exist, and higher nutrient deep waters often well up and mix with surface waters, creating a much more productive ecosystem that results in cloudy water.

Here is a map from NASA showing productivity of world oceans:
http://science.hq.nasa.gov/oceans/living/sensing.html

Here is an explanation about tropical thermoclines:
http://www.biosbcc.net/ocean/marinesci/04benthon/crform.htm

Answer 2

It is due to the tides and rip currents. The stronger they are the more sediment they pull up off of the bottom making the water "dirty". All the water looks the same about 20 miles offshore.

Answer 3

Turbulence and the amount of suspended solids and other debris in the water.

Answer 4

Stop peeing in the ocean, and don't drink that yellow water.

Answer 5

i think it's mainly related to the land underneath the ocean, of course pollution (from us), and rivers that empty into that ocean.

Answer 6

geomorphology of the area.