Underwater Navigation

[gcbryan]

Just set the compass bezel in a relative sense straight out and the tail of the compass will be "up top" on your way back...in addition to all the other good advice already given. It really is just a matter of some more experience and paying attention.

 

[Hatul]

My method of navigation is to set my compass before descending to point to shore (or some other stationary landmark) and leave it there until the end of the dive. That's my reference direction.

When I swim I look at my compass to see which way I'm swimming in relation to my reference direction and form a mental image of my dive pattern. If I'm swimming 90 degrees from my reference direction I have to swim the opposite to return. If I don't find the anchor line to make the safety stop I do the blue-water safety stop and surface to take a bearing on the boat to return.

It's a simple system that works and does not require fiddling with the compass or counting kicks and works in the poor vis waters of California and even in night diving, shore and boat diving.

I set the compass once at the beginning and once at the end to correct to get to my target.

Adam

 

[TSandM]

An addition to what TSandM posted: When you swim away from the anchor line, turn around and look at it from a short distance away. You may remember it was next to an outcrop of coral but you want to know what the outcrop looks like from the direction you will be heading on your way back. It's also nice to know what's beyond the anchor line so you can have a complete picture in your mind of what the surroundings should look like as you near the line.

Good point, Ber!

I can empathize with the comment about getting lost in a closet. I'm the only person I know who has set out to swim along a depth contour (on a definite slope) and has managed to swim around in circles! But I really think the key is where you put your attention.

I did a boat dive a couple of years ago in Southern California. I was diving with two local people who had done the site before. The dive consisted of a whole bunch of rock ridges on a flat, silty bottom, covered with kelp. Then there was a silty area that ran to the rocks on shore. Viz was about 20 feet or so (so you couldn't see the shore) and the anchor was dropped on featureless bottom maybe ten feet from the nearest rock. I was in the middle of the team, and we set out and zig-zagged back and forth through these rocks and kelp for about 20 minutes. At this point, the guy in front turns around and signals to me, "You're #1"

I had, of course, been hunting nudibranchs and octopuses, and paying only desultory attention to where we were, because I was going to follow HIM back.

I got us somewhat close to the boat, and when I finally gave up and admitted I was lost, he pointed above us.

I told the story to point out that lack of attention is the biggest reason for getting disoriented, and that you have to use ALL the available information (including shadows) to figure out where you are.

 

[ajduplessis]

AmRus,

I also struggle with navigation using the D9 digital compass. It is way to sensitive, switches off every 60 seconds and there is the possibility to reset the bearing leaving you "screwed" (need to write it down on slate to combat this). I would recommend getting analogue compass for navigation, and only if you do a lot of navigation dives. The D9 compass should only be used as backup.

 

[DiveNav]

..... The DM signaled to me to end the dive with my partner and recover via the RIB, while the rest of the group continued the dive......

excuse me for asking .... but what is a RIB?

..... I am completely disoriented underwater. I really think I passed the AOW part of navigation only by luck.....

I had a similar problem when I started diving several years ago .... that is way I started to create my own 3d maps of dive sites and the simulator to dive them

Another trick I learned is to note the depth as soon as I descend .... of course this does not help if the bottom is flat ... no contour lines there to follow.

 

[AmRus]

Thanks. At the end of the day, I agree that it's mostly been dependency on the DM - and that with practice I'll get this down. Just wish I had more time for practice!

 

[AmRus]

My apology - in this forum I try to remember not to use non-standard shortcuts. In our case, diving from a live-aboard in the Red Sea, we would often anchor some distance from the dive site and use Rigid Inflatable Boats to convey/recover the divers. They were Zodiaks.

 

[Diver0001]

I have the same problem with boat dives in unfamiliar places!

You can do a lot of navigation using natural features. For one thing, if you are diving off an anchored boat, make careful note of the depth where the anchor is sitting, and what the terrain around it looks like. (For example, is it sitting on top of a knob, or on a flat, sloping bottom, or in a pile of boulders?) Where the bottom has a distinct slope, you can pay attention to whether you are swimming with the shallow side on your right or on your left (getting home is the reverse). Most of our Red Sea dives were either on or near walls, or on sloping bottoms (or on wrecks, which are their own navigational landmarks). A compass is helpful if the visibility is too poor to orient on surrounding landscape, or if the bottom has very little slope or is extremely irregular.

Time can also be useful. If you know you swam 20 minutes in one direction, then the anchor line isn't likely to be more than 20 minutes back (unless you were swimming with, and then against the current).

Noting unusual features that you pass can help reassure you, too. I've even been sure I'd found the spot for the exit because we swam over the same furious nest-guarding fish we passed on the way out! My husband did some navigation in his IE by nudibranch But anything that's likely to stay put and be recognizable is a way to reinforce your orientation.

I guess what it comes down to is that good navigation requires pretty good situational awareness, which means noticing more of what's around you than the particular fish or coral or sponge that's caught your eye. As a guided diver, you don't have to do this much, but as an independent diver, it's key.

Another great post.

AmRus, you can learn this. It's just a matter of using things you already know and to put it together.

In addition to the advice I quoted in the post above, I'll just give you a couple of pointers.

1: you *need* to have a mental map of the dive-site to understand how to dive it. If you don't know if the bottom slopes off, if it's a wall, which compass direction the dive will begin in, which compass direction the current is running etc. then you dno't have enough information about the site to "recognise" things that you're seeing. Part of your problem, therefore, is not knowing (or asking) enough questions about the layout of the site.

2: Lynne already said it, but I'll say it again. When you don't know where you are, then time and depth are your best handles for navigation. Assuming no (or very light) current, if you follow a particular depth line for a certain length of time at a given pace and then turn around and follow that same depth line (or another one, maybe shallower) for the same length of time in the other direction, then you *will* end up where you started. I use this technique a lot where I dive (we have vizibility in the 3 metre range) and after a dive of an hour or longer I can literally come out of the water within spitting distance of where I want to be. One dive I recall, my buddy asked me where we would come out and I pointed at a particular stone and said, "right beside that stone". After an hour we surface literally right beside that stone and the student found it uncanny. It isn't. I can get lost in a closet too. It's technique that anyone can learn. Once you get this technique down you'll start to see how you can build on that for more complicated dive plans.

3: you need a real compass. That Suunto computer has a lousy compass. It's hard to read and very sensitive for tilting, which makes it inaccurate. Get a good-old-fashioned mechanical compass and wear it on your wrist.

R..

 

[fnfalman]

Practice, practice, practice. I think that underwater navigation is probably the hardest skill for a beginner to learn and harness because the beginner is innundated with many tasks and probably doesn't have much left in the mind for processing additional information.

I was lucky because I was a US Army soldier for a long time and was pretty good with land navigation. The same techniques apply underwater with minor variations. One of my dive buddies was a US Army Ranger and his navigation skill is uncanny. I don't think he ever used his compass at all yet we always ended up at the same place by the end of the dive.

 

[Hatul]

AmRus,

I also struggle with navigation using the D9 digital compass. It is way to sensitive, switches off every 60 seconds and there is the possibility to reset the bearing leaving you "screwed" (need to write it down on slate to combat this). I would recommend getting analogue compass for navigation, and only if you do a lot of navigation dives. The D9 compass should only be used as backup.

I've wondered about the digital compass because I was interested in the Cobra 3, so last night I printed the manual for the Cobra 3-- the 3 pages on the digital compass. From what I could gather the digital compass is not for me. It's fine for following a bearing but that's not how I use the compass most of the time when I dive.

When I dive I need to form a mental image of my dive pattern and the analog is much better for this. And there is no need for precision.

Adam