Tides and Dive Planning/ Execution

Can anyone recommend any articles related to dive planning/ execution in areas where tides are an important factor? As well as any explaining why tides affect certain areas more than others? Google's not turning up anything decent, just little snippets of info.

I'm not planning any dives in those sorts of areas, but I'm curious, since tides aren't really a factor here. Except occasionally when they're very low, which makes launching little RIBs difficult (since the water isn't at the slipway).

It's current you really want to plan for ... and although the size of the tidal exchange provides a rough idea of what to expect for current, it's not necessarily the best planning tool. I have to log off now and get ready for work ... I'll try to dig up some resources for you later, unless someone else has already provided them.

... Bob (Grateful Diver)

NWGratefulDiver:

It's current you really want to plan for ... and although the size of the tidal exchange provides a rough idea of what to expect for current, it's not necessarily the best planning tool. I have to log off now and get ready for work ... I'll try to dig up some resources for you later, unless someone else has already provided them.

... Bob (Grateful Diver)

Click to expand...

Thanks very much. I also have to run out now, but I was thinking after I'd posted my question that if no-one knows of any nice resources, I could type out my current understanding (gleaned from various bits and pieces on the internet) and see if SBers can fill in the blanks or correct me where I'm wrong.

blue Heron Bridge is highly dependent on the tide tables

The impact of tides varies greatly by location. In some areas it won't make a noticeable difference. In other areas it is crucial.

One factor is the depth of tidal change, which has a lot to do with latitude. An area that is a great dive at high tide can be undiveable at low tide.

Another factor is the topography of the area. As the tide comes in and out, if there is a narrow opening, it can create strong currents going one way as the tide comes in and the other way as the tide goes out. Blue Heron Bridge, mentioned above, combines both of these issues (depth and current). Look at a map of Puget Sound and try to imagine what the tide moving in and out of that complex geography must do to the currents.

It is really hard to make a comprehensive guide to tides in general because of this local variability. When I went to Puget Sound, I relied very heavily upon local divers telling me where the best diving would be at the time I was there. On another occasion I went with another diver to California, and he had planned the whole trip. He did not realize that one (and only one) of the dive sites he had chosen was very tidal dependent, and on the day he chose to dive it, low tide (undiveable) was smack at noon, pretty much making a decent dive day there impossible. There is no substitute for getting local knowledge when diving in a new area.

In general, areas adjacent to large embayments and estuaries are best dived on an incoming tide. The reasoning is the rising tide will wash clean oceanic water into the embayment. Outgoing tides will flush eutrophic bay- and harbor-water out and by the dive site. These large bodies of trapped moving water also tend to produce larger currents around pinchpoints at their mouths as can be seen in the Bay of Fundy and Long Island Sound. Also, incoming tides often (but again, not always) tend to carry the diver toward land and presumably the intended exit.

My experience is that etides accentuate surge where suurge is prevalent, and dives at the time of high and low tide have less surge in areas prone to surge. Tides can also increase or create current. We always check with a local when doing shore dives alone to get the tide schedule and their take on impact.
DivemasterDennis

You need local knowledge. What applies in one place with tides/currents may not be the same somewhere else.

For a good general background and grounding in the subject do a search for some of the BSAC (British Sub Aqua Club) "Dive Leader" material - I think some of the lesson notes and slide shows are open source.

Tides and currents are critical to most UK diving and is very heavily covered in the BSAC syllabus, including chart reading, working out high and low tides, and current "slack times" based on marine charts.

The BSAC boat handling syllabus also covers this in great detail (I did my course last year) and is really good for understanding the principals behind it all. - The names of the relevant skills development courses which might help the search are -
Diver Coxwain
Boat Handling
Chartwork and Position Fixing

If you can't find any info let me know, I should still have my course notes and might be able to point you the right way - Phil

Thanks for all your replies. I should've guessed that the reason I wasn't getting satisfactory answers from Google was the way in/ degree to which tides affect diving depend very much on the area and specific site.

Phil_C, thanks, I'll have a look around for those BSAC materials.