Clear Ocean Water


Active member
Jun 27, 2009
Not sure if this is the right forum, but how is it that ocean water in some parts of the world is clear and you can see to the bottom? How would the chemistry makeup register on a pool test kit? I'm assuming the chlorine would have to be at zero, yet no algae is present.


LifeTime Supporter
Aug 20, 2009
North Central Texas
How about a few people, going on tropical vacations, take a testing kit.

Inland lakes occasionally become over populated with algae, due to many different reason, but frequently because of pollutants, "over feeding" the algae.

Frequently, the visibility of ocean water has to do with weather conditions and how much bottom sand/silt is being stirred up by the ocean tides, currents, waves, etc. So turbidity of water is not necessarily due to the presence of algae.

In healthy bodies of water there is a balance of organisms that keep the algae in check. Without algae, though, the oceans would probably die, beginning at the bottom of the food chain, where the smaller animals consume only algae. Larger consume those and then on up.


chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
See this link for example (it has several interesting links within that article). Take even "clear" ocean water (or fresh water) and look under a microscope and you'll be amazed at what you see. It takes quite a lot of algae to grow before it becomes visible as dull or cloudy water. This is why you will usually see a higher-than-normal chlorine demand before you see the water become less clear.


Platinum Supporter
LifeTime Supporter
Apr 14, 2010
Stephens City, VA
geekgranny said:
How about a few people, going on tropical vacations, take a testing kit.

Ok. I'll cover Cozumel end of July. As well as the cruise ship pool and kid soup pot (hot tub).

Incidentally, I've always enjoyed the ocean. For some reason it's natural way has never led me to feel as unsanitary or heebie jeebied out like some lakes do. And, lakes like Erie, Michigan, and other larger systems don't seem as icky as the smaller stripper pit type (gravel pits).

The exception is if the shoreline LOOKS polluted with foam, scum, OIL, etc.


LifeTime Supporter
Feb 26, 2010
Guam, USA
OK, I'll bite :) I live on the tropical island of Guam, and the water (the ocean and our pool :cool: ) is VERY clear. Tomorrow morning when I head out diving, I'll grab a sample before I come home and post the results.

PS... For all you divers out there, visibility at most of Guam's dive sites is usually 50-100+ ft. :-D

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