Current Woes

Sasquatch · Post by **Sasquatch** » Thu Sep 14, 2006 8:27 pm

I'm trying to get a grip on the art and/or science of predicting slack tide around these parts. I've made my piece with tide and current books and the adjustments you make from sources like Northwest Shore Dives.

But, I'm hoping that by posting this I can stimulate some wisdom on the topic. Does everybody use the same system? Do most of you dive the slack or just avoid big exchanges? If the ebb or flow is going to be over a certain speed you avoid it but if it's a knot or 1.5 knot you go for it?

The whole current thing is weird to me. On a recent thread LG asked about the difference between EUP and the Edmonds oil dock. The corrections for the currents were quite different between the two places though they aren't that far apart. Then I looked at the corrections between EUP and Mukilteo (a much further distance between these two sites) and the corrections were the same! Then, later in that thread LG mentioned she and some folks were shooting for a slack at 6:55 PM. Dude, I went over my books, charts, internet and did my calculations and I could not find a 6:55 slack anywhere for the Oil Dock at Edmonds.

Here is my sad story. What's the answer? I'll just do what I do unless someone can come up with some insight or technique I've overlooked. Otherwise just don't depend on me to predict slack.

Sea ya!

Joshua Smith · Post by **Joshua Smith** » Thu Sep 14, 2006 9:27 pm

I'm really glad you posted this. I grew up in the desert, and I don't know a damn thing about tides. I'm always nodding like I agree with whoever's talking when they yammer on about flood this, and exchange that, but I don't know much except the water moves around a lot, and swimming against it doesn't work very well most of the time.

(Sits down next so 'squatch and waits for a smart person to enlighten him)

jeff98208 · Post by **jeff98208** » Thu Sep 14, 2006 9:42 pm

asi await some one to show me how to read those aswell, i am forced to join squatch and nailer awaiting for some one to show us how to read those.

](*,)

aLittletank · Post by **aLittletank** » Thu Sep 14, 2006 10:09 pm

Great topic!

now move over, I need a seat in this class as well.

Allen

Aquanautchuck · Post by **Aquanautchuck** » Thu Sep 14, 2006 11:41 pm

](*,) ](*,)

To funny. Hey been there done that. A few years ago I took a dive planing class and it helped real well. To answer a few of your questions.

You get to know what sites you really need to pay attention to for current. If the books say when to dive that is when you should dive. There are several places I watch real close when diving on my zodiac. Some of them are real current intensive places and you do not want more than a knot of current. Some of them are China Wall, or Blake Rock, Watermans Wall, South side of Blakely Island, Sunrise Beach, Titlow, Alki Pipeline can be nasty with current, and the Oil Dock. This is just some of the examples.

As for what do I use to figure slack out. When I started diving there where not any of the web sites to look up tides and currents. I used a tide book to just so so luck. I then found Nobeltec's "Tides and Currents" software. It is awsome and I have used it for years. With a good set of charts so you can find reporting stations and their numbers it works for me. Some of the web sites to get the tides and currents are:

http://www.noaa.gov/
http://tidesandcurrents.noaa.gov/tp4days.html
http://tbone.biol.sc.edu/tide/
http://www.saltwatertides.com/

I am the first one to admit the only place I have problems at is Sunrise Beach. That place just confuses me and half the time I get it wrong.

Anyway, Move over and make room for me. Hopefully someone will know more than me.

Charles

gcbryan · Post by **gcbryan** » Thu Sep 14, 2006 11:46 pm

OK, class, please be seated. Look up (online or in a book) Admiralty Inlet and you will see that slack before flood this evening occurs at 7:07pm. Look at the correction for Edmonds Oil Dock for slack before flood and you will see that it is - :10 therefore slack would be 6:57pm.

In general with sites that get a lot of current it's best to dive them at slack only on mild to moderate exchanges. The further off shore (if doing a shore dive) the more mild the exchange should be (Day Island). You could dive Sunrise at slack with a little higher exchange because you aren't so far from shore meaning you can also end the dive easily if necessary.

What else do you want to know?

Class dismissed.

gcbryan · Post by **gcbryan** » Thu Sep 14, 2006 11:52 pm

Charles, I just saw your post after I posted. Regarding Sunrise basically that's one site where the corrections in Northwest Shore Dives is incorrect.

The key to that one is to look for the current station at Gig Harbor. If doing as a shore dive, get into the water about 20 minutes before slack as it takes several minutes to swim down the beach to the drop down point. Once I'm there I stay in shallow water and simply stand up and watch the surface current. It usually starts to slow down as the Gig Harbor station predicts and then I do the dive. It usually works well for me.

If you do it on a very high exchange day you will be dealing with some current no matter what you do more than likely.

gcbryan · Post by **gcbryan** » Fri Sep 15, 2006 12:07 am

On rereading the original post maybe you are looking for something even more basic.

Flood:water coming in from the ocean through the Straits of Juan de Fuca.
Ebb: water going out

It's not always obvious which is which depending on the individual location but look a the graphic representation in the TideLog book for example. Flood is when the curve is upward and ebb is when it's downward. If there is a large curve (great difference between high and low tide) then that would be a large exchange. If the curve is flatter then it's a moderate or mild exchange.

Tides and currents are not the same but are closely related. On the outer coast they would be the same. Here in the Sound currents very since it takes the water differing times to get from the ocean, down the Strait and around various land features. Thus the need for individual site correction factors.

All you really need to know is the name of the current station nearest your dive site. You can find these online (see Charles post) or you can use TideLog and charts or anything you want.

If there is a fair amount of current known to be at a certain site then you only dive at slack or on a very mild day off slack. If it is a place like Cove 2, 3 Tree N., Les Davis, Lobstershop Wall, Sund Rock, Redondo, then you can dive it most any time. Day Island needs to be done on a milder day, Deception Pass needs to be done on the mildest day (s) of the year. You get the picture.

The bottom line is know your dive site.

Any questions class?

DiverDown · Post by **DiverDown** » Fri Sep 15, 2006 2:31 am

I like to use the tide log... I buy it at UWS, It gives you all the info you need as long as you know how to read it.. I think some one here on this board gives a tides and current presentation??

Pez7378 · Post by **Pez7378** » Fri Sep 15, 2006 7:50 am

I brought my own chair, the bench looks crowded. I'm with you guys. It seems like this is another basic skill that no one learned in OW. This is why we rely so much on each other. We were conditioned to do that. Go with someone who knows how rather than learn how yourself.

Excellent topic.

Sounder · Post by **Sounder** » Fri Sep 15, 2006 8:41 am

Sorry I'm tardy - I'll try not to let that happen again.

I think it would make a great topic for another NWDC pizza night! My house is always available on the eastside on Pine Lake (on the Sammamish Plateau) but I would be a student NOT an instructor.

GillyWeed · Post by **GillyWeed** » Fri Sep 15, 2006 10:13 am

There is a tides and currents class... I saw it at Federal Way UWS once... I was busy with my advanced course so I didn't have time to take it... I am bringing my chair too. I am paranoid about getting caught in a strong current.

Grateful Diver · Post by **Grateful Diver** » Fri Sep 15, 2006 10:18 am

GillyWeed wrote:There is a tides and currents class... I saw it at Federal Way UWS once... I was busy with my advanced course so I didn't have time to take it... I am bringing my chair too. I am paranoid about getting caught in a strong current.

Steve Fischnaller (the author of Northwest Shore Dives) used to teach one ... not sure if he still does or not, but it was excellent. There's also some good material in the front section of his book that explains how to use current tables ... and the descriptions of the dive sites in the book include time corrections for calculating slack.

Janna also used to do a tides and currents class ... again not sure if she still does or not. All I see advertised anymore are critter classes.

... Bob (Grateful Diver)

thelawgoddess · Post by **thelawgoddess** » Fri Sep 15, 2006 10:39 am

i found this while i was searching around one day: http://www.bio-marine.com/classes/dpct_tut.html ... i haven't had a chance to "do" it, but i have it saved on my computer to review soon. from a quick skim, the material looks nice and simple.

some other nice stuff on that site - including a currents worksheet. it also looks like that site would normally list above-mentioned type of class, but there are none listed on their calendar at the moment. maybe someone could contact the website owner and see if they'll do one for the club?

i learned some about tides/currents back when i sailed a lot, but i find it more of an issue with diving because i can't just turn on my motor to help me out ...

Sasquatch · Post by **Sasquatch** » Fri Sep 15, 2006 11:02 am

Most of the little knowledge on this subject I have I got from reading Northwest Shore Dives. The information in the front of the book was most helpful in explaining how the process works and the specific site descriptions show corrections and flow direction during flood and ebb.

There have been some good answers and information in this thread. Does anyone want to try to explain why the corrections between Muk and EUP are the same where as the correction from EUP and Edmonds Oil Dock are so radically different when they're so near each other?

So, today I see slack before ebb at 1347 (1:47PM) with a correction of +13 minutes for Mukilteo. So slack is at 1400 (2PM)?

Edmonds Oil Dock, slack before ebb, is 1347 (1:47PM) with a correction of -1:32 making slack at 1215?

EUP slack correction is the same as Mukilteo.

Have I got this or am I still confusing the "before ebb/before flood" times?

And a pizza meeting sounds good now that the days are gettting shorter. Everybody got their Christmas shopping done?

Zen Diver v1 · Post by **Zen Diver v1** » Fri Sep 15, 2006 2:43 pm

Yep, Stephen Fishnaller still teaches it, I believe, and also Nicolle Pratt, as well as Mishi Carter of Pelagia Scuba. All good classes and instructors.

-Valerie

Aquanautchuck · Post by **Aquanautchuck** » Fri Sep 15, 2006 4:27 pm

Hey has anyone got a cushion for this bench? My butt is getting tired.

I have a pretty good grasp of figuring out when to dive. Its the terms that are thrown around that are confusing sometimed. I have seen 4 different phrases used in the same dive site diving instructions.

Like why don't they say something simple like low tide slack or high tide slack. Instead of slack before ebb or slack before flood or high slack or low slack. Isn't slack before ebb the same as high slack and slack before flood low slack? ](*,) ](*,) I need to sit down again, where's that cushion.

Charles

CaptnJack · Post by **CaptnJack** » Fri Sep 15, 2006 4:40 pm

You got it.

Slack before ebb = "high slack" (a bad term)
Slack before flood = "low slack" (again, confusing tides and currents)

I recommend the current atlas, it will really help understand some patterns, eddys, etc. There are 2 volumes: one for the sound and one for the straits and san juans. Available via Steve Fischnaller's website.

RJ

Sasquatch · Post by **Sasquatch** » Fri Sep 15, 2006 4:52 pm

OK, this link from The Law Goddess is very good. I feel slightly smarter now...

http://www.bio-marine.com/classes/dpct_tut.html