Underwater navigation

[Nwcid]

I have done plenty of land navigation and I understand the principles of underwater nav. I understand how to go in straight lines underwater and using reciprocal headings. Of course I need lots more practice at all of it.

We have only done 2 dive days on our own and were practicing skills during that. At one point we decided we were going to swim around the edge of a little cove out into the main body. After swimming for a bit and not feeling like we were where I thought we should be we surfaced (about 20'). I found we were about where I thought we were direction wise but about 100 yards further out then I thought. What is the trick to determining distance underwater?

After that we decided to swim back to the dock. Instead of making a straight line to the dock there is a marker buoy there too. We figured out roughly the heading change needed from the buoy to the dock. Of course swimming form a point you can find to the next worked very well and we were able to hit both of our marks.

So I guess my main question is how do you tell distance and how do you nav without fixed points to go off of? Or can it be done?

 

[tbone1004]

know how far you can go on one kick and count kick cycles. only real way to do it but it takes patience to figure that out right. Using those stupid compasses on the consoles is a surefire way to get lost though. Making a simple slate with a $10 sylva compass from wally world works just fine. If I remember I'll upload a video on how we make ours tonight. You could also use a reel with distance markers on it. Just knots tied every 10-50-100 ft or however accurate you need it

 

[Nwcid]

See even with line, just like reciprocal headings it is only good to go straight in and straight out. What if you want to go to muliti points or swim a circle?

I have a regular Sylva but was kinda worried it might have issues with water and pressure.

So I guess the better question would be how do you nav without getting lost without going in straight lines in and out?

 

[Akimbo]

Unfortunately, counting kicks or estimating kicks based on time are the only viable methods short of expensive and bulky acoustic technology. Both require a lot of attention and discipline, both in counting and maintaining a consistent kick. Compensating for current is another real-world complication.

Really accurate underwater navigation is distracting enough to make it decidedly not-fun and is too lofty a goal for recreational divers. Following a compass within 20° is often adequate before poking your head up to make corrections. Spend most of your attention enjoying the scenery. We’re not combat swimmers after all.

 

[FinnMom]

You can try a triangle or rectangle. That's not too challenging and lets you see new territory the whole time. In small quarrys and lakes I usually just remember what corner (NE or SW for instance) my entry point was at or near and navigate that way, also taking a good look at what the underwater terrain near the entry point looked like. Practising underwater navigation can make it very entertaining to dive the same small place quite frequently.

I've also found that it's easiest to navigate with the compass secured to the back of my hand. Replace the original strap with a couple of bungees. Bungees make it easy to secure and remove the compass to wrist for storage and to your hand for careful navigating. Watch out about getting distracted and dropping the compass! I suggest brightly colored bungees to make it a tiny bit easier to see the thing if you do drop it. Also remember not to start swimming like an olympian when you are following a heading. It's too easy to forget all about your buddy and no fun for the person left struggling to keep up w/ no time to look around and enjoy the dive.

 

[Jim Lapenta]

In addition to what FinnMom said you can also use time and air pressure to keep track of distance. I use this almost exclusively for longer swims as kick cycles get too hard to keep track of once I get over 25 or so. I swim slowly so using time is a good indicator. I also like the compass on the back of my hand with my bottom timer right next to it on the wrist. Above that is a small wrist slate. On one arm in a nice line is all the info I need to perform nav. I do suggest though for those just starting out that you do not try to do everything on your own. I have been working on Nav skills for nearly 7 years now. I've written a Nav course and it's the one I teach.

The three biggest obstacles to UW Nav are trying to take on too much of the task by one's self, not communicating effectively, and going too fast.
1. You need to share the load with your buddy.
2. If you are watching the compass they keep track of time, depth, and points of interest.
3. You need to talk over the tasks before you get in the water and keep the communication open throughout the dive.
4. You need to go slow enough to see points, keep your buddy in proper position, and go slow so that you can stop and do precise turns.

Big looping turns introduce error. In some cases that is ok if you are dealing with current. It can be used to compensate for it.
Precise helicopter turns minimize error and help hold courses true.

Lines can be used for circles, u - patterns, and if you know how to do tie offs (which I teach in my course) you can do some really complex navigation with great confidence and safety. You just need to look back at where you came from and take note of the heading from each tie off.

 

[Scuba_Noob]

If you take the PADI Advanced Course, there's a part on Underwater Navigation. It's adequate, but nothing beats experience. At first, there's a lot of task loading when you add the compass in with buoyancy and other skills, so maybe you'd want to be very good at the other major skills first.

Even after learning how to use a compass in the Open Water class, I wasn't able to use it well until I continuously practiced through numerous dives. Don't always go on dives where you're just following someone. Trust your compass, determine how many fin cycles (one kick per foot) it takes for you to go a certain distance, and don't worry about being off by a bit (you can always surface swim).

 

[Colliam7]

So I guess my main question is how do you tell distance and how do you nav without fixed points to go off of? Or can it be done?

As others have said, for distance, use kick cycles, or time. Jim also mentioned air consumption, which can be used as well. If you want to know something about YOUR swimming style, and how much distance YOU cover, you can take a 100' tape measure into the water, lay out a relatively straight, even depth 100' line, and swim it four or five times. This will give you a rough idea of how many kick cycles it takes YOU to go 100 feet. In addition, take a watch / timing device (a second hand / digit helps) and figure out how LONG it takes YOU to swim 100'.

That way, you can get a rough idea of how to tell distance underwater. It is a coarse measurement. Currents can affect it, you level of energy can affect it, etc. But, it is much better than pure guesstimation, and it actually works.

As for navigating without underwater markers, a combination of compass headings and distances is the most viable alternative. Of course, you have to have a reasonably good idea of what leg headings and distances are. Now, a combination of compass navigation, and natural navigation is also useful, IF it is practical. For example, in our local quarries, we know something about headings to where various u/w objects of interest are, and can swim a particular heading from a starting point to a recognizeable u/w point, and change heading to get to a final destination. Prior knowledge is necessary, of course.

 

[RonFrank]

I have done some fairly advanced navigation. It's a guessing game at best, but you can use depth, UW landmarks like bare areas, gravel areas, grass, muck, etc. We often try and go out 100 yards, turn 45 degrees and go another 50 yards, turn 45 degrees and head back to shore. Its obviously best to do this in places you have been before. If not just surface as need be.

If doing this in a place for the first time a sneak and peek maybe necessary. IMO exact UW navigation is next to impossible unless there is awesome vis and well defined landmarks. I can usually do well on a reef for the first time, but I have also lost my bearings and had to do a sneak and peek. There is nothing wrong with going to the surface to get your bearings during a dive assuming you're diving shallow (10-50ft). I skip the SS and am back down in seconds. Granted most dives do not need much navigation to be successful.

 

[Nwcid]

Thanks for all the pointers guys. We only got 2 local days in before the snow hit. While I would like to go again not sure I am up for snow diving. We might make it over to the coast once this winter if we are lucky. We are going to Hawaii in May and plan on getting a couple of dives in, but was not a dive trip when planned cause we were not divers yet. I am just trying to get as much good info as I can to practice when I do hit the water again. Once spring is here we will be getting wet every chance we can and practicing things like this in the local lakes.