Sand ridges for navigation

[icechip]

Yesterday diving off Lincolnville Beach in Maine and I noticed lines of sand ridges on the bottom once we got a decent distance from shore. It got me to wondering about their reliability and/or usefulness as a possible navigation aid, if necessary, maybe if even in just a general sense?

 

[BoltSnap]

These "sand ripples" are certainly one of the key tools for natural navigation underwater. They are "generally" parallel to shore (but can be at an angle depending on the water movement, or currents, in the area) and get closer to each other when you get closer to shore. They provide a clue/sign of where the shore is and how close you are to shore.

 

[T.C.]

Yesterday diving off Lincolnville Beach in Maine and I noticed lines of sand ridges on the bottom once we got a decent distance from shore. It got me to wondering about their reliability and/or usefulness as a possible navigation aid, if necessary, maybe if even in just a general sense?

View attachment 447465

If you note how they run in relation to your course, they can be useful for navigation, but should not be relied on for more than that dive. Conditions may change from day to day and dive to dive. In heavy surge, it may not be wise to rely on them at all.

Instead, note what fish is directly below your boat or entry point and look for that fish when you return. This method cannot fail.

 

[TMHeimer]

I have used them as well. Pretty safe bet in the ocean off Nova Scotia that they'll be parallel to shore. Not so much with narrow inlets (like the FL panhandle) with swift tidal currents.

 

[ermaclob]

For the most part i used them on beach dives and shallow water boat dives ~ 30 ft, here in Miami where i live the run north to south so you know that west (shore) is perpendicular to the lines.

I will say however that there can at times be inconsistencies in there direction if you are around some sort of large object such as a ship wreck or topographical object as large rocks or reefs can change the flow of water on the bottom and change the direction that the lines are made. I have a suspicion that in deeper water currents don't have the same consistent effect on the sand as in shallow water. hence i don't rely on the sand lines in deep water.

also keep in mind when using the lines that if you get disoriented an lose your general sense of direction you will still have to decide between 2 possible directions using the sand lines to lead you to shore or your boat. i find the best thing is to have a compass and use the lines in conjunction with it to get a good sense of direction underwater.

 

[JamesBon92007]

They are fairly consistent off the shore in Southern California and run parallel to shore (usually). So, when navigating, if you are swimming perpendicular to the ridges you are either swimming toward or away from the shore. That's when your depth gauge can be used as a navigational tool--it usually gets shallower closer to shore.

 

[TMHeimer]

also keep in mind when using the lines that if you get disoriented an lose your general sense of direction you will still have to decide between 2 possible directions using the sand lines to lead you to shore or your boat. i find the best thing is to have a compass and use the lines in conjunction with it to get a good sense of direction underwater.

Yeah, I forgot about that. I have on rare occasions been concentrating on what I'm looking for and had that 50-50 dilemma.

 

[Sam Miller III]

I agree with @JamesBon92007--wave formed ridges are generally always present UW on not only SoCal but all west coast beaches

Sand Ridges are often referred to as "Natures Navigation" and extremely useful for shallow water and on occasion deep water UW navigation but the diver, like the tracker of old, needs to know how to read them which often varies by location,depth and force of the surface wave action.

Generally the front of the UW ridge, the side towards the beach will be gradually sloping.\towards the beach, however this will vary according to depth and wave action. In deeper water or areas of gentle or minimum surf areas the ridges will almost demonstrate equal angles

Generally the back of the ridge facing towards the beach will be more pronounced with a steeper angle and often have debris deposited on the slope or in the valley, However once again in deeper water or areas of gentle or minimum surf areas the ridges will almost demonstrate equal angles

They are always 90 degrees to the prevailing wave direction.

If over a sandy area or soft sub strata and sand dollars are present, they can be in colonies or singular and generally lined up 90 degrees toward the shore so as the maximizes their filter feeding abilities, In rough water or in areas of periodic excessive wave action often will burry into the soft sub strata or the soft sand.

So discouraging that so many divers only have been trained and have the ability to dive down, swim around and swim up. To advance and become more enlighten they will need to enroll in course after course taught by a fuzzy faced instructor who can read upside down water than the student can read right side up

I can visualize a new specialty "Sand Navigation" it is only $$$$$

SDM

 

[MaxBottomtime]

Sometimes they can mess you up. Most beaches have sand ridges parallel to shore. At Marineland in Palos Verdes they are, until you get far enough from shore. The prevailing westerly current then pushes them perpendicular to the beach. I made a mistake once when swimming out to a submerged platform off Marineland. After visiting the platform I checked my compass so I could lead the dive back to the beach. I kept looking at the sand ridges and stopped trusting my compass. Big mistake! We exited the water two coves east and had to walk on rocks and surface swim another half mile. It was a long day. The longer line represents where we exited thanks to me following the sand ripples.

 

[Steve_C]

Don't remember which one? Solo, Nav, OW, AOW, probaby Nav, but I remember a course where sand ridges were mentioned/in the book. I checked and it is mentioned in the SDI solo manual.