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In yesterday’s post I wrote “Do trust your charts and your eyes when entering through the dangerous reefs here instead of looking for the charted navigational aids.” Hopefully you can trust your charts but at times, even they can be inaccurate. If you learn to read the water though, and the conditions allow it, you can’t go wrong.

But what specifically should you be looking for? Here is what we have learned about the waters of the Bahamas and the Caribbean. Although there may be exceptions, the color of the water typically varies from dark blue for deep water, to an aqua color for shallower areas to a bright yellow for really shallow spots. Although dark patches in the water could be just sea grass on the bottom, they could also equal coral heads which can reach dangerously close to the surface, even if the surrounding water is 20′ deep. Another danger tell-tail is water breaking over just-submerged reefs. Avoid that as well.

What allows us to see these things? A combination of good sunlight, calm sea state and awareness. Avoid entering into any areas that require you to read the water if the sun is low, and especially if it is in your eyes. You have much better visibility when the sun is high. This often means that you will need to schedule your arrival at a new bay to allow for this. On that note, scattered clouds can often be confusing as they cast dark shadows on the water which sometimes look like coral heads. Not dangerous by themselves but they do confuse things.

Calm, clear water is definitely preferred over choppy seas as the latter can disguise the waves breaking over dangerous reefs. Murky water could also hide rocks and other nasties.

Lastly, you need to be aware and paying attention. Posting a lookout on the bow, or perhaps at an even higher vantage point, makes reading the water much easier. We always do this when entering, or leaving through sketchy entrances. As with all things nautical, practice makes perfect.

The different water colors and the location of the coral heads are easily viewed in these photos. If you look closely you can see small patches of white which are waves breaking over the reefs.

Although I don’t recommend anyone doing this, the only way we were able to zip around in between the reefs in the video below was because the sunlight and conditions allowed us to easily view the location of the coral heads.


  1. What about polarizing sun glasses? Or are the differences more obvious than that?

    I sail a good bit on parts of the coast where the charts are rather useless. Some of the Chesapeake can be like that too, particularly between some of the islands where the channels wander a lot. Even with the muddy water there are still subtle differences, and when the sun is low polarizing glasses help.

    a word of warning; on the Chesapeake darker can mean deeper if the changes is gradual, or shallow with grass if the change is abrupt! At least it’s all soft. All that coral would make me a wee bit nervous.

    • It makes us nervous at times too!

      I don’t really know how polarized glasses help. People say that they do but I don’t know if I’ve ever had a pair.

      • Yeah, they help a lot.

        When light reflects off water, for the most part ONLY the waves that are in the vertical plane reflect (think of light as waves going up and down, but in 360 dregree rotation). This is also true of glare off roads and other cars. The polarizing lens is like blinds and clips off the light from the vertical plane (reflected light) but passes the more diffuse light, reducing reflected glare by perhaps 80%. You can see into the water better, because the reflections are gone. Fly fishermen swear by them. Very good when the sun is in front of you.

        They are generally labeled, but they are easy to test; if you rotate the lenses of 2 pair at 90 degrees from each other they turn nearly black, because they clip light both ways.

        They also make LCD displays very hard to read (they are based upon light polarization). I’m surprised you havn’t played with a polarizing filter on your camera–they make seas darker, skies darker, increase contrast in clouds, and increase color saturation–not that this is better, but it’s something to play with and something to google.

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