Dive Planning

[archisgore]

I know there was mention of a workship a few years ago, but I was not a diver then.

I was wondering if there are resources I could read/study or take a weekend crash course on how I would go about planning a dive specifically with regard to currents.

What are Tide Tables? What are Current Tables? How do they work? How do I know is a lengthy slack?

Let's take the example of the most awesome dive - Deception Pass. (Don't worry I'm not a fool - I'm not going to secretly go there on my own at some odd time.)

I know this last September 28th at 11:40 splash was a "good time". By what standard? How would I do the math and come to the same numbers?

[selkie]

Step one, think about just how much current you can handle. For most divers .25 to .5 kt of current is more than enough. This will change if you are doing a drift dive. When planning it is best to have an idea of the limits you do not wish to exceeded.

Step two, find this book and read it. 2009 Pacific Northwest Current & Tide Tables for Dive Planning (2009, Mischi Carter)
I am pretty sure it is out of print and do not think Mischi is doing current seminars any more.

Step three, dive some current sensitive sites with divers experienced with those site. Be sure to go through the book and do the calculations for the planned dive. Soon you will start to understand why the experienced divers picked the times they did. If you don't get calculations that look right ask questions. DO NOT just rely on someone else calculations without doing your own.

Over time you will adjust the answer to step one and become confident at planning for currents.

Always remember current planning is a prediction not a hard science. Topography and bathymetry can cause localized effects not planned for. Observe the water before entering. Ask local divers for local knowledge.

Good Luck,

[Jeremy]

Let's take the example of the most awesome dive - Deception Pass.

I know this last September 28th at 11:40 splash was a "good time". By what standard? How would I do the math and come to the same numbers?

Get a grip man!!! Are you crazy???

[spatman]

+1 to everything Selkie posted above.

Let's take the example of the most awesome dive - Deception Pass.

I know this last September 28th at 11:40 splash was a "good time". By what standard? How would I do the math and come to the same numbers?

Get a grip man!!! Are you crazy???

Maybe you'd like to clarify your post by explaining to the OP (and the rest of us) why that would be "crazy".

[Jeremy]

Nah....he sounds like a psycho, probably wouldn't listen to reason.

[fmerkel]

What 'selkie' said is a generally functional construct. You have to know how it works before you can apply specifics.
How you apply that information is site SPECIFIC. Most sites in the Sound will not have the same variables.
What applies to Deception does not apply to DIW, is totally irrelevant for Skyline, and won't work at Sunrise. You have to know the principals, then you have to work out how THAT site works. More experienced divers for that site can save you a whole lot of grief figuring it out the 'hard way'.

[Mortuus]

+1 to everything Selkie posted above.

Let's take the example of the most awesome dive - Deception Pass.

I know this last September 28th at 11:40 splash was a "good time". By what standard? How would I do the math and come to the same numbers?

Get a grip man!!! Are you crazy???

Maybe you'd like to clarify your post by explaining to the OP (and the rest of us) why that would be "crazy".

Lol.... Pretty sure Jeremy's post was intended as humor. He and Archis are pals

[archisgore]

Jeremy is hardly a voice of reason. :-P

[H20doctor]

the best way to learn currents is to get in touch with an experience diver.. and have him show you, I use two tide programs, dariki, tides and currents.. and if that doesn't work I call one of my friends... so I would plan a dive site to dive and post here for help, .. there are few sites here in the Northwest that need good tide planning..

[archisgore]

Thanks for the guidance all. That's precisely what I want to do - learn from experienced divers and make my own plans to compare. At some point I have to learn to make my own current decisions in addition to blindly joining a posted event.

[CaptnJack]

At some point I have to learn to make my own current decisions in addition to blindly joining a posted event.

Ask the host of each dive you attend to explain why that day and time is "good".

Steve Fischnaller's book explains most of the popular shore sites with graphics. Worth getting even though its out of print.

[WaGigKpn]

Tides are big slow waves. They are estimates and can vary depending on weather. The most accurate tides are the ones at the reporting station, the farther from the reporting station, the less accurate the tide prediction. Using your 9/28, 11:40am example...


There are two 'types' of tides (excuse my vocabulary, i dont know the lingo). There is a big exchange and little exchange which alternate. You can see that in the graph. When diving current sensitive spots without a dive boat you want to dive on slack leading to a small exchange. That way if something goes wrong and you are in the water longer than planned you wont have the strongest currents to deal with. As you can see, 11:40am is before slack which then leads to a small exchange.

Another factor is direction, this is site dependent so pay attention! on an incoming tide (Leading to high tide) the current at deception will be running from west to east, from the shore entry spot toward the bridge. Considering when you are done with your dive you are swimming back to the same entry point you would want to enter the water at the tail end of the flood, do your dive during slack, and return as the tide shifts to an ebb (going out). If you were to dive at a low tide you would fight the current out and then fight it back in...a fight you WILL LOSE at deception pass...

Each site is different, high current areas are around points and choke points...Slack at these places will not be as long as open areas such as bays and main bodies of water.

Lastly, Weather patterns can have HUGE effects on tides and current causing them to be different than predictions. (Anyone correct me if i am wrong) If there is a low system OVER Puget Sound the tides will be higher and high tide will be later than predicted. If the Low is off the coast then Tides will be shorter and happen earlier than predicted.

This leaves us with 11:40am on 9/28...I have not dove deception pass but the place interests me greatly...on a fair weather cycle with no low pressure systems influencing, I think 11:40am is a tad early, maybe 30 min to an hour early for a 40-60min dive on an AL80 to OW depths. that being said, its better to hang out in the protected water waiting for the current to slack than to be late and miss your window all together! You also may want to be there that early because you have a group of people and inevitably someone is going to have last minute issues thus giving some wiggle room. If your dive is going to be longer than a rec dive then you would start earlier as well...Maybe on that day there was a low pressure system approaching thus adjusting the tide prediction? Finally, since i have not dove that site, maybe it is a site specific thing where the current changes before the tide prediction hits high tide. Just because it says high tide at a certain time does not mean the current changes at the same time....try fishing on the straight...Current takes 2 hours or more to catch up to the tide.

Hope this helps....I am self taught so the experts can chime in and correct me if i made a mistake...

[WaGigKpn]

EDIT:

I forgot the #1 thing to say regarding currents...DO NOT SWIM HEAD ON INTO CURRENTS IN AN EMERGENCY! YOU WILL RUN OUT OF ENERGY QUICKLY!

If you find yourself off course and the current working against you you have a few options...Swim perpendicular to the current toward shore or safety. If that is not an option, stay calm and conserve body heat while you wait for rescue...Your suit gives you a long time before dangerous hypothermia becomes a real threat. To conserve body heat, try to curl up in a ball.

Lastly, if you have air or are mid dive and the current picks up. Follow your heading to safety (ie shore). Dive down and Hug the bottom and crawl along with your hands, boulders and obstacles have a great back flow behind them where you can seek shelter and rest. Being able to get your body on the floor creates suction pushing you down and you can make good progress into the current without spending much energy. This part i am speaking from experience.

[Mac]

Here's something you may be interested in.

http://www.nwscuba.org/class_descriptio ... ss_id=3137

I took it a couple years ago, and found it useful. Part of the class teaches you how to decipher the black tide-log book and adjust for your location.