Scuba With Bill

As an instructor who teaches underwater navigational skills and someone who reads more than his fair share of scuba industry related publications (and websites, and message boards, etc.) I’m always a little surprised that I rarely see mentioned what I consider to be one of the more useful tricks of the trade so I thought I would share it here.

First off, let me start off by admitting that I’ve gotten lost before. In fact, when I first started diving it used to drive me crazy when I surfaced where I thought the boat was and I was waaaaaaaaaay wrong. Partly because I consider myself to be a tad of a land navigation expert. When I served in the Army part of my job was to evacuate injured troops with my only way of finding them being a set of grid coordinates, a map, and a compass. I’ve even set up and helped judge night land navigation competitions so this underwater thing should be no problem, right?

Well, that’s what I thought. See, on land you have a couple of things working in your favor:

1. Visibility

2. The ability to travel in straight lines.

Underwater visibility can make navigation tricky. You probably have better visibility on a well lit evening than you do in 30 foot viz on a mediocre diving day.

And this is the key to the tip I promised; underwater it’s difficult to travel in straight lines. Sure, you can travel along a compass bearing but you’re only on track for as long as you’re staring at your compass. Since most of us dive to enjoy the scenery there’s a pretty good chance we’re going to take our eyes off the compass now and again during the dive with anything from surge to current to just plain mentally zoning making you swimming off course until you check your compass again.

So let’s say you do a simple out and back pattern. You swim out for some predetermined amount of time or air supply and then you double back on the reciprical compass heading. If you’re off on your compass bearings 30% of the time (which is being pretty liberal) you’re 30% off on the way out and 30% off on the way back. Depending on the conditions that put you off course that could mean the difference between surfacing right under the boat and being a couple of hundred yards from it.

So how do you keep on track? Well, in the Army you shot a compass bearing and then you picked out a land feature that was dead on your compass bearing and when you got to that land feature you took another compass heading and lined up another land feature.

The same can be done underwater. Instead of following your compass the entire dive just shoot a heading and then look for something very specific on that heading. It could be a rock, the opening in a kelp bed, or anything else that isn’t likely to move between the time you take a compass heading and the time you reach it. Once you’ve got that feature picked out you can zig zag all over the place, do flips or anything else you want between point A (where you started) and point B (the point on your compass heading) because you can see where you need to go. Once you’re there, take another compass heading and keep going.

Obviously you would do the same thing on the way back but once you start getting good at it you’ll be able to pick many of the same points on the way back in as you did on the way out so if you remember that on the way out you swam from the rock to the old tire, on the way back when you get to the old tire you may not even need to take a compass heading if you can see the rock and know that that’s your next navigation feature.

It’s pretty simple once you get the hang of it. Give it a try on your next dive.

In August edition of Rodale’s ScubaDiving they quote a survey in which 25% of the people polled admitted to jumping in the water, at least once, without turning their air on.

I can only guess the same rule of thumb that applies to peeing in your wetsuit is going on here:

50% of divers admit to peeing in their wetsuits. The other 50% lie about it.

I’ve never quite made it into the water forgetting to turn my air on (thanks to some thoughtful divemasters and the fact that I make it a habit to take a few breaths off the reg before I enter the water) but I’ve had a few buddies (and other instructors) swim up to me and sheepishly ask if I could turn their air on for them.

Despite this perfect record (chuckle), my worst mental lapse was when I got to the gate to exit the boat and the divemaster just looked at me. I put my reg in my mouth as I asked “What?” and she replied “You’re not going in like that are you?” I did a quick pat down of my gear thinking I might be twisted up or something and upon finding everything in it’s place I said “Sure, why?” “Well, unless you’re going to go running along the bottom you’re probably going to need your fins,” she replied. Lucky for me I was one of the last divers off the boat so that incident stayed our little secret.

Last weekend while I was diving with a buddy we got to where we were going to exit and I looked down at my computer which was indicating that I had already surfaced from the dive and that I was enjoying a surface interval. Now, as I was a good 20 - 30 feet below the surface I was pretty sure I wasn’t at the surface so I punched a bunch of buttons on the computer thinking it might come to its senses.

It was only then that I noticed that the battery meter was registering in the “need to be replaced mode.” The funny thing is that for the last several years I’ve carried a backup computer somehwere on me just in case but almost felt foolish for doing so. Not this time though. I reached in my drysuit pocket and my backup was working perfectly.

I had remembered what my now impared computer had said was my maximum depth during the dive (and had a general sense for the total dive time) and compared that to the backup and they seemed to match so it was a relief that I hadn’t been getting faulty readings and had been diving much deeper than I had thought I was but still an eye-opener that just because a computer goes into dive mode on descent doesn’t mean that it’s got enough juice to see you through the entire dive.

So the lessons learned here are:

a) Check your computer’s batteries every couple of years or so.

b) It’s always good to have a backup.

On a side note (that I almost feel foolish admitting); on my backup computer it has a voltage reading. If it goes below 2.8 I know to replace it. On my primary computer it has a bar graph that displays when you first begin your dive. I always check the voltage numbers on the backup and replace at 2.8 even though it could probably go all the way down to 2.0 before it becomes an issue. On my primary, I don’t think I ever really checked it because it only displayed for a few seconds when going into dive mode at the beginning of the dive. That’s a mistake I won’t make twice

An interesting little story on spearfishing from depths of 200 feet or more.