Here's a little brain twister. All the information needed to answer the questions is provided in the story.

Distance
Speed * Time

The quiz is all about relative motion and distance, speed, time calculations. It shouldn't be easy unless you have a nautical slide rule and have done this sort of thing before. I'll do my best to show how I arrived at the answers if anyone wants to know.

Thirty-miles east of Fictitious Inlet a boat drops three divers into 90’ to spearfish and bug hunt; it’s 08:34 in the morning. All three are diving with HP100’s and expected dive times are ~30-minutes. Seas are 2-3 feet and the wind direction is a steady 10-knots out of the southwest. The current is 045-degrees from the drop point at a speed of 1.3 knots. The divers’ bubbles are hard to follow, but it’s apparent to the Captain his divers have gone opposite directions on the ledge, which runs due north and south. The Captain elects to keep the outboard motor running and maintain the boat’s position on top of the bubbles nearest to the jug.

At 09:00 Diver #1 pops up due east of the jug and he’s bitching about fighting the current. At 09:04, Diver #2 surfaces northeast of the jug, but there’s no sign of Diver #3. After hauling Diver #2 aboard, the Captain checks the time on the GPS, it’s 09:07 and Diver #3 should be up by now. Neither Diver #1 nor Diver #2 has seen Diver #3 since hitting the water. It’s 09:10 and the search is on.

Thirty-six minutes earlier, Diver #3 was the last one over the side and the first two divers were already headed down the jug line while he was still loading his speargun bands. Instead of kicking toward the jug, Diver #3 did a slow descent to the bottom and upon reaching 60’, realized that he was over the sand with no ledge to be seen. Diver #3 knew the ledge would be up current and started working his way to it. The swim, however, proved more difficult than he anticipated causing him to over-breathe his regulator and subsequently get lightheaded. It was at this point Diver #3 decided to abort the dive.

Diver #3 obeyed his computer and ascended at the programmed rate of 30-feet per minute and followed that up with a three-minute safety stop at 20’. When Diver #3 broke the surface it was 08:40; he had an elapsed dive time of six-minutes and he was approximately 250-yards from the boat. He blew his whistle, but the Captain couldn’t hear it over the outboard. He then inflated his four-foot, blaze orange safety sausage, clipped it to his speargun and waved it, but the Captain didn’t notice it in the morning sun’s glare. Diver #3 looked at his watch, it was 08:46 and he was 500-yards from the boat. He knows nobody will be looking for him for at least 20-minutes and wonders why he never got around to vacuum sealing some flares.


1. What course should the Captain steer to find Diver Three?
A. 225-degrees
B. 090-degrees
C. 045-degrees
D. 345-degrees


2. At 09:10 when the search begins, which answer best indicates the distance Diver #3 has drifted from the drop point?
A. 1600 yards
B. 1200 yards
C. 800 yards
D. 600 yards


3. The Captain begins a 6-knot, straight-line search at 09:10 towards the drifting diver. Which answer best indicates approximately how long will it take to overtake Diver #3?
A. 3-minutes
B. 10-minutes
C. 15-minutes
D. 17-minutes


4. How far will the boat be from the drop point when they reach Diver #3?
A. 1300 yards
B. 1600 yards
C. 2000 yards
D. 2500 yards


5. How many nautical miles would Diver #3 drift in six-hours?
A. 9.8 nm
B. 7.8 nm
C. 6.6 nm
D. 5.2 nm


6. 10 pt. Bonus! If someone based the calculations for Question #5 on miles per hour instead of knots, how many yards would the error amount to after six-hours?
A. None
B. 410 yards
C. 830 yards
D. 1440 yards

wow..
I dunno but you can bet I'm gonna learn..

I threw some fluff in it to make it more difficult...sorry.

The most important calcs in my mind are knowing the course to steer to find the diver (045) and when you will overtake his farthest possible position.

We know the current was 045 @ 1.3 knots. Since nobody has a confirmed position of Diver #3 other than the drop point, we have to use that position and that time to start the plot. It's also the reason it is very important to record the GPS time that divers hit the water.

So, it's 09:10 and diver three hit the water at 08:34....36 minnutes.
We know the Speed...Diver #3 is drifting at 1.3 knots.

One way is to convert the time to a decimal. We do this by dividing 36 by 60 to get .6
Using the formula for Distance you would multiply speed and time 1.3 * .6 = 0.78nm... To get yards, multiply .78 * 2000 = 1560.

Yes, it's a pain in the ass to do all of that calculating and the chance for an error in a high stress situation is high.

Here's where this cheap piece of plastic comes in handy.

http://www.chesapeakemarineinst.com/store/nauticalsliderule.jpg

The Nautical Slide Rule is someting we should all have in our boats. It's the best way to quickly and accurately solve distance speed or time problems. You just line any two pointers up on the data you know and you have your answer.

So we know Diver #3 is between the drop point and 1600 yards away, bearing 045 degrees. So we take off at 6 knots in that direction and begin to overtake Diver #3. Using the same formula or the slide rule, it's going to take us about 9 minutes to reach 1600 yards. But Diver #3 is drifting away from us at 1.3 knots, so in the 9 minutes it takes us to get there, he will actually be farther downcurrent by another 400 yards.

We should find Diver #3 1950 yards (50-yards short of one nautical mile) from the drop point at about 09:20. That's a long way to drift in the span of 36-minutes and my whole idea with this "exercise" was to give an idea of how far and how fast someone can get away from us if this kind of scenario ever happened. Knowing how to figure these problems will hopefully help us locate a diver quicker and also allow us to coordinate with the other boats in the area that we've called to assist us.

Some may ask "why not use a GPS"?
GPS units are only good for navigating to a fixed point and will NOT take you to a moving object. They will provide data, yes...but they won't solve the problem for you.

I'm sorry if my explanations are confusing; I'm not a very good teacher. But I promise if you get a Nautical Slide Rule and play around with it you will be able to solve these kinds of problems fast. If I can help anyone some more with this stuff, just let me know.

Interesting scenario, I was real close to 1, 2, 3 without the ruler. Your explanation is good too.

In that equation, where do you put the 90 minute variable while you sit on the surface and post on SB while your diver is missing?

In that equation, where do you put the 90 minute variable while you sit on the surface and post on SB while your diver is missing?


You don't bother, because you know the diver isn't on the surface, so why waste your time looking?

But it is OK to allow everyone else to have a false sense of hope and allow them to do extensive surface searches, wasting time and money and worst of all the hope of finding the diver alive.

OUCH

Interesting scenario, I was real close to 1, 2, 3 without the ruler. Your explanation is good too.

You would have found your diver, Roland. :beer:

Spearchucker and bgbill's comments, while pointed in a direction I'd rather not go in this thread, do bring up a point. When do you make "the" call?

Had I been the captain during this scenario, my call for assistance would have gone out at 09:10, the same time I started looking for my diver.

When do you make "the" call?

I can't see a valid reason for waiting more than 15 minutes, even if you don't want the Coats Guard too start the search, they can at least start getting ready.

The CG does not sit on a pad with the help running waiting for a call to find someone, they have to have time to mobilize, one of the helos came from St Petersburg, it takes a little while to fly across the state.

Part of the problem I see with Tony is, he seems to loose quite a few divers on the surface for extended periods, so he may not call the CG immediately if at all, I wonder if he called the CG when he lost divers in the past?

If you call the Coast Guard and put them on standby or even if they deploy, you can always call them back once the diver is found.

Would you want to be drifting at sea in a ripping current while a guy waits 45 minutes to over an hour and half to call the Coast Guard?

I know if I lost a diver for 45 minutes or more, I would fully expect an ass whoopin' when I finally picked them up, if there are mechanical issues or weather issues, that is a different story.

Thirty four years of diving on both coast of Fla.i have never lost a diver.But i have lost plenty of equipment.throwing two weighted flags at spaced intervals will give you the approximate drift and easy to follow direction to recover diver or equipment.

Thirty four years of diving on both coast of Fla.i have never lost a diver.But i have lost plenty of equipment.throwing two weighted flags at spaced intervals will give you the approximate drift and easy to follow direction to recover diver or equipment.

I used to dive over in the exact same area that Nikki was diving in and have run a boat as well and have never lost a diver.

My wife even ran the boat while my buddy and I dove, and the weather turned to shit, but she managed no to lose us, my GF prior to me meeting my wife would run the boat and she never lost us either, neither one of them had ever run a boat before.

I don't think I have ever had a diver wait on the surface more than a few minutes for me to pick them up.

You make me wait on the surface for 45 minutes or more without a very good reason, we will have issues.

Thirty four years of diving on both coast of Fla. I have never lost a diver. But I have lost plenty of equipment. Throwing two weighted flags at spaced intervals will give you the approximate drift and easy to follow direction to recover diver or equipment.

The drift diving that's done down south is a little different than what we do up here. Typically, I'll jug the ledge and drop divers so they can follow the jug line to the bottom. The current is variable and does not necessarily run parallel to the ledge. During mini-season we had a 1.7 knot current that was running due east while we were diving a ledge that was oriented north/south.

When we would start our ascent the current would immediately pull us off the lege and to the east. A standard six-minute ascent would put us 350-yards east of the ledge when we surfaced. Fortunately, it was slick calm and it easy to stay on top of at least one diver's bubbles. Add a 2'-3' chop and it makes things more interesting.

Trigger Happy, your idea of throwing weighted flags at spaced intervals is good stuff. That information along with knowing the exact dive times/expected surface time is key to staying on top of what's happening. Nobody should ever have to wonder, "what time did they go in the water?"

As a freshwater diver,I find alot of this maritime stuff facinating.I mean,when a guy throws outta dive report and relays pea soup vis,I can relate.However,surfacing from a dive finding myself adrift and in a bad situation is,quite frankly,a scenario I've never really played out before,let alone having to find a drifting diver.I'm somewhat embarassed to say that. So,anyway,good thread peeps.:)

Something else that's a pet peeve of mine is the use of "miles-per-hour" instead of "knots". It's not the same.

Charts are printed in nautical miles. The Coast Guard and every other professional maritime agency communicates distance in nautical miles and speed in knots. The difference in the quiz question is 1440-yards...a huge error.

2000 yards = 1.0 nautical mile
10 knots = 10 nautical miles per hour
10 nautical miles = 20,000 yards

You can change your GPS in the system setup menu usually under "Units" or "Distance".

Use of miles-per-hour on the water should be limited to the glitter boats.

If you are diving with somebody,especially on the east coast,and the Capt.and crew is not looking after his divers you had better seriously consider making your LAST DIVE with those BOZO'S

LC GREAT info..I'm getting the slide rule tomorrow..

I agree with Bgbill & have called the CG when my diver about 5 years ago thought it was fun to see how far he could swim under water, I found him after I threw a weighted jug (was all I knew at the time) to figure out the drift. It worked - I found him about 5 min after I called once I convinced them all was well they stood down. The wind had kicked up pretty good and was almost oppisite to the current. 15 min overdue & called 5 min later found him.