When walking along the perfectly sandy beach in the Bahamas, you will notice small ripples in the sand. At low tide, these can come out of the water creating what almost looks like a fingerprint on the shoal.
These sand ridges are actually caused by the oscillation of surface waves as they come upon the shore. Based on depth and wavelength, the period between the ridges can be determined. This also means that if waves are consistent, so will the ridges in the sand.
Areas where the ridges differ from the norm or run at a new pattern are indicative of changes in the wave period as it approaches the shoar.
Another cool thing, especially if you encounter these ridges at low tide, is they will tell you which direction the waves were coming from.
The ridges always have the short side facing the direction the waves were moving towards and the long side facing the direction the waves were coming from. In the picture above, you can see that the long sides are to the right, and the short side is to the left. This means that the waves that formed these ridges were coming from the right and running from right to left.
This information is useful if you are walking along an exposed sandbar and want to know where the waves will be coming from as the tide returns. All you need to do is look at the ridges!