Navigation pointers

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Jon_R

Contributor
Messages
211
Reaction score
53
Location
Palm Bay, Florida
# of dives
50 - 99
Newly certified. To date I have done shore dives and drift dives. Drift dives boat finds you and shore dives it easy to find the shore might not be the exact spot you entered but can find land. This weekend we did a boat dive where boat stays. The plan was go out against the current turn and come back with the current. Fair enough I understand headings and can use a compass but how do know how far back is the boat. Current was not extreme but certainly was decent. I overshot the boat about 300 yards after surfacing and looking around for it. The we had to go against the current back to it.

Is it just experience or are there some tricks? It can't be swim out 25 minutes then back 25 minutes given going with and against the current.

Always looking to learn.

Sent from my iPad using Tapatalk HD
 
On the way out look around and take note of what you see. Before you leave sight of the anchor line, turn around and look at it from the perspective of what you'll be looking at on the way back. Take note of anything that would be recognizable ... like some structure that you'll be able to identify on the way back. Note depth at the anchor line before you head away from it ... depending on bottom topography it might be possible to swim back at that depth until you get back to it. Keep a "mental map" in your head of which direction you go away from the line ... and try to reciprocal that heading on the way back. Most of all, if you're unsure, err on the side of surfacing "upstream" of the boat. As you just found out, heading back into the current at the end of a dive sucks ... especially if you're getting low on air at the time.

... Bob (Grateful Diver)
 
Above are good points.

Another is before you set off explore around the anchor. Look for recognizable structures on either side.

Another is what is the viz? That tells you how much room for error you have.

Personally, if the viz is low and there are not really obvious navigation makers I will run a reel. That's what they are for.

Case in point, I was leading a group of three, the other two being instructors on a 15 ft high broken up ledge in 100 ft of water. Viz was about 3-4 ft. I violated both my suggestions above. Went a short distance and headed back. We spread out along the ledge so we covered about 15-18 ft. We went back and forth twice. Never did find the anchor. Turned out it was behind a rock at the top of the ledge. So it was open water ascent time. About 30 ft up the water went clear and I could see we had spent the whole time within a short distance of the anchor. Lessons learned.
 
A few more tips for diving off an anchored boat in current . . . One, you might want to limit the distance you move from the anchor line. You can use a spoke or star pattern to go out and come back repeatedly, rather than swim steadily away from the anchor for a long period of time. Of course, if you are on a linear reef structure, that may not work, but that should be an easy setting in which to find the anchor on the way back.

Second, as has already been said, make sure you LOOK at the site where the anchor is lying -- note the depth and the type of structure. If you are following a linear reef and you come back at the depth where the anchor is, you should encounter it or its chain.

If you do make a linear track away from the anchor into current, try to estimate how strong it is -- do you just notice it, but if you stop swimming you don't move much? Or is it strong enough to require some effort to swim against, and strong enough to move you backward the minute you stop kicking? In the former case, I'd probably note the time at which I turn, and start looking for the anchor five minutes or so before reaching that time. In the latter case, I might start looking halfway through the "back" time, or less.
 
A few more tips for diving off an anchored boat in current . . . One, you might want to limit the distance you move from the anchor line. You can use a spoke or star pattern to go out and come back repeatedly, rather than swim steadily away from the anchor for a long period of time. Of course, if you are on a linear reef structure, that may not work, but that should be an easy setting in which to find the anchor on the way back.

Second, as has already been said, make sure you LOOK at the site where the anchor is lying -- note the depth and the type of structure. If you are following a linear reef and you come back at the depth where the anchor is, you should encounter it or its chain.

If you do make a linear track away from the anchor into current, try to estimate how strong it is -- do you just notice it, but if you stop swimming you don't move much? Or is it strong enough to require some effort to swim against, and strong enough to move you backward the minute you stop kicking? In the former case, I'd probably note the time at which I turn, and start looking for the anchor five minutes or so before reaching that time. In the latter case, I might start looking halfway through the "back" time, or less.

All of that, and add to use a line. If you have a reel - you can also use a spool, just more of a pain to reel in - it becomes very easy to find your way back to the anchor line.
 
A few more tips for diving off an anchored boat in current . . . One, you might want to limit the distance you move from the anchor line. You can use a spoke or star pattern to go out and come back repeatedly, rather than swim steadily away from the anchor for a long period of time. Of course, if you are on a linear reef structure, that may not work, but that should be an easy setting in which to find the anchor on the way back.

Second, as has already been said, make sure you LOOK at the site where the anchor is lying -- note the depth and the type of structure. If you are following a linear reef and you come back at the depth where the anchor is, you should encounter it or its chain.

If you do make a linear track away from the anchor into current, try to estimate how strong it is -- do you just notice it, but if you stop swimming you don't move much? Or is it strong enough to require some effort to swim against, and strong enough to move you backward the minute you stop kicking? In the former case, I'd probably note the time at which I turn, and start looking for the anchor five minutes or so before reaching that time. In the latter case, I might start looking halfway through the "back" time, or less.

That being said I would dive with you anytime , I know we're on the same page good advice!
 
I believe the biggest issue is viz.

If you are in the Caribbean with 60 ft visibility and a nice sloping contour, them all you have to do is come back at the anchor depth. Since the book is anchored in 30 feet of water and you can see 60 ft you should be able to see the boat as you approach it.

Welcome to vacation diving.

Otherwise you need to have a higher navigation skill level. Definitely look backwards as you head out and also pick at least 2 reference points that you will look for as you return. They could be coral heads, cuts in the reef or just simply sandy spots. Make sure you understand what your reference points will look like from above as you will likely be above them on your return.
 
One of our most difficult sites is a silt plain with virtually no depth contour, studded with concrete chunks and rebar that were dropped as an artificial reef. Even without current, it can be virtually impossible to find your way back to the anchor, and it's impractical to run a line, because the chunks of structure are far enough apart that you wouldn't see much before your reel was empty. Since the viz is typically about ten feet, you almost have to plan for a surface swim AND have a boat tender who can come get you if you screw up badly enough. This is another place where scooters are handy, too!

It's also important to talk about gas planning for anchored boat dives, because if you HAVE to get back to the boat, you may have to plan a much more conservative approach to your gas management than you do when you can surface anywhere you want. I've done more than a few dives in Southern California, where we missed the anchor line and had to do the prairie dog maneuver of popping up to take a bearing on the boat, and then dropping to ten feet to swim under the kelp canopy. It's nice not to have any pressure of low gas supplies if you have to do that.
 
As others have already mentioned natural navigation where you take a mental note of "home" where the anchor is and try to pick out a unique structure you will recognize when you come back. Also, for me at least, the depth is a big help in getting you close to home especially if you are diving where the bottom slopes. In addition to the compass reading take note of the depth. As you descend then ascend back up the slope then you will have a better idea of where you should be when you get back to your starting depth.

Kick cycles help where you count how many kicks you swam out, then count the same coming back. Keep in mind that the distance you cover going out against the current will be somewhat shorter than with the current so it won't be completely accurate but will put you back in the ball park.

I've heard of divers using PSI where you go out certain amount of air and then come back about the same. I've never used this but have heard of others using this technique.

Also, especially if viz isn't good, you don't have to go out too far from the boat. There should be plenty to see around the reef where you dropped anchor. Spend time peeking in the crevices for small creatures hiding. My personal favorites are octopuses, but my daughter has been really good at finding small nudibranchs. You can't be running all over the reef like it's a long distance marathon.
 
https://www.shearwater.com/products/swift/

Back
Top Bottom