This is a continuation from Compass basics... The Lubber Line and Compass Basics... Navigation Exercises.
OK, now we have the operational portion of the compass down pat. Let's start discussion additional clues we have underwater.
Managing currents... As we know there are three types of currents: Standing, transitional and tidal. The Gulf Stream is a well known standing (permanent) current. A longshore current (caused by wind) would be a transitional (non-permanent) current, and the ins and outs of the tide are our third current. We are going to concentrate on transitional currents here, though much of what will be said is applicable to all currents.
Finding a current while diving off of a boat is simple. Look at the anchor line. USUALLY, swimming past the anchor is swimming into the current. Just to check this stop kicking for a moment after you have descended and look up. Which way are you going? The surface wind can make the current appear to be in one direction while being at depth takes you in yet another direction. It is almost always advisable to start your dive INTO the current, and be sure to take a bearing as you start. You are going to want it on the way back!
Shore diving usually gives us a mix of transitional and tidal currents, with the most worrisome being the longshore current. Now a longshore current is caused by a wind that does NOT hit the coast line on a perpendicular. The current is usually generated towards the obtuse angle of incidence. Now, we can try to see something floating in the water to determine this current, but that is often not the case. So, before you enter the water pick a couple of exits to your left as well as to your right as alternates in case you don't get back to shore in the same spot. This is especially important when diving in rocky areas where getting out can be a real problem.
Once in the water, you can often tell quickly which way you are headed by the movement of the sea floor under you. In a sandy area, simply look at the ripples in the sand. They reflect the waves and are perpendicular to the current. If these ripples are parallel to the shore, then you have no real longshore current. That can change as the wind changes and the ripples do take time to change to the new current. Personally, I head out perpendicular to these ripples and head in on the reciprocal course. Take a reading to be sure. The deeper the water the less likely it is to have significant ripples.
Now, there are other aids to navigation while under water. Rocks, reefs, ledges, walls and the like will give you an easy way to go out and to come back AS LONG AS you can recognize the feature on your return. So, as after you pass a landmark take a few seconds to turn around and LOOK at it from the return perspective. Note the depth and any unique features it may have if you want to just say "NO" to long surface swims.
You can even use the sun as a guide. Sure, it's position will change a bit during your dive, but for the most part it will still provide a rough check for your navigation. If the sun is on my left as I go out, it should be on my right as I come in.
Navigation with a buddy. The best bet here is to take turns. Sure, check each other's work but with each dive, the other buddy should be "in charge" and that means navigation too! You should ONLY do dives where both buddies have the training AND the experience to complete. Avoid those "Trust Me" dives.
Hopefully, we will have some questions and more input on this topic! I just ask that we stay on course!
OK, now we have the operational portion of the compass down pat. Let's start discussion additional clues we have underwater.
Managing currents... As we know there are three types of currents: Standing, transitional and tidal. The Gulf Stream is a well known standing (permanent) current. A longshore current (caused by wind) would be a transitional (non-permanent) current, and the ins and outs of the tide are our third current. We are going to concentrate on transitional currents here, though much of what will be said is applicable to all currents.
Finding a current while diving off of a boat is simple. Look at the anchor line. USUALLY, swimming past the anchor is swimming into the current. Just to check this stop kicking for a moment after you have descended and look up. Which way are you going? The surface wind can make the current appear to be in one direction while being at depth takes you in yet another direction. It is almost always advisable to start your dive INTO the current, and be sure to take a bearing as you start. You are going to want it on the way back!
Shore diving usually gives us a mix of transitional and tidal currents, with the most worrisome being the longshore current. Now a longshore current is caused by a wind that does NOT hit the coast line on a perpendicular. The current is usually generated towards the obtuse angle of incidence. Now, we can try to see something floating in the water to determine this current, but that is often not the case. So, before you enter the water pick a couple of exits to your left as well as to your right as alternates in case you don't get back to shore in the same spot. This is especially important when diving in rocky areas where getting out can be a real problem.
Once in the water, you can often tell quickly which way you are headed by the movement of the sea floor under you. In a sandy area, simply look at the ripples in the sand. They reflect the waves and are perpendicular to the current. If these ripples are parallel to the shore, then you have no real longshore current. That can change as the wind changes and the ripples do take time to change to the new current. Personally, I head out perpendicular to these ripples and head in on the reciprocal course. Take a reading to be sure. The deeper the water the less likely it is to have significant ripples.
Now, there are other aids to navigation while under water. Rocks, reefs, ledges, walls and the like will give you an easy way to go out and to come back AS LONG AS you can recognize the feature on your return. So, as after you pass a landmark take a few seconds to turn around and LOOK at it from the return perspective. Note the depth and any unique features it may have if you want to just say "NO" to long surface swims.
You can even use the sun as a guide. Sure, it's position will change a bit during your dive, but for the most part it will still provide a rough check for your navigation. If the sun is on my left as I go out, it should be on my right as I come in.
Navigation with a buddy. The best bet here is to take turns. Sure, check each other's work but with each dive, the other buddy should be "in charge" and that means navigation too! You should ONLY do dives where both buddies have the training AND the experience to complete. Avoid those "Trust Me" dives.
Hopefully, we will have some questions and more input on this topic! I just ask that we stay on course!
