Help With Tide Table

[Former FLL Now MSP Diver]

There's a popular dive site near me that should only be dived at slack tide. I understand that's when the tide isn't coming in or going out and there's not much current.

Is slack tide either at low tide, or high tide? According to the schedule below, would I want to be in the water at 10:03am? Or some time period before and after high tide?


Saturday, May. 3, 2003

4:17 AM EDT Low Tide 0.42

6:40 AM EDT Sunrise

10:03 AM EDT High Tide 2.67

4:23 PM EDT Low Tide -0.05

7:53 PM EDT Sunset

10:42 PM EDT High Tide 2.90

Marc

 

[jiveturkey]

Slack high tide by rule of thumb is usually the best time to go. You'll find your vis to be the best at that time. However, you should check with a local diver who knows the specific conidtions of that dive site. It's possible that there may be some unique conditions that you should be aware of.

 

[Rick Murchison]

Slack tide is at high tide & low tide. Where a bay is involved, visibility is generally better at high tide, as ocean (or gulf) water is usually clearer than the bay. (there are exceptions)
Usually, a plan that has your entry and exit evenly spaced around the slack is best, so, given the table you have, for a half hour dive you'd start about a quarter to 10 and exit a quarter after.
It is also a good idea to spend at least one tidal shift at your potential dive site with tide table in hand before you dive it, observing the current and recording the actual slack, then comparing it with the table. Rarely is the dive site and the tide datum site the same, and the specific timing of the tide at your dive site will vary somewhat from what the official table says - and the variance can be significant enough to make a difference in when you should time your dive.
The good news is that usually the timing difference is pretty consistent. The bad news is that it ain't necessarily so, particularly if there's some substantial wind involved. Be flexible, be observant.
Rick

 

[TwoBitTxn]

I think this is what Rick was saying but,

Tide tables are generally published for a specific spot or small area. There is normally a correction table posted along with it.

i.e. I am used to seeing tide tables with Alabama Point as the reference. There was always a correction table along with it stating +/- so many minutes for your section of coastline.

TwoBit

 

[Jonathan]

be a map with your tide table that shows you which way and how strong the currents are going. This is usually in hourly intervals.

As a rule of thumb usually high or low tide time +/- 30 minutes - but that is not always true.....

Jonathan

 

[Rick Murchison]

TwoBitTxn once bubbled...
I think this is what Rick was saying but,

Tide tables are generally published for a specific spot or small area. There is normally a correction table posted along with it.

i.e. I am used to seeing tide tables with Alabama Point as the reference. There was always a correction table along with it stating +/- so many minutes for your section of coastline.

TwoBit

Right, and even the +/- spot can vary from the dive site, so it's a good idea to watch a cycle yourself and actually see when the current is slack at your intended dive site (make a correction to the correction) before making the plunge.
Rick

 

[Charlie99]

Most tide tables are for water HEIGHT, not current. If you can't find a table for current, then you will have to use some combination of personal observation, info from locals, and guessing.

If there is just a small inlet into a very large bay, such that the bay water height lags the ocean significantly (and has much reduced tide amplitude), then slack water could be as much as 3 hours after high and low water.

If the water height in the bay varies in height almost as much as the ocean, and it lags the ocean just a bit,then slack water will be just a few minutes after high and low tides.

Obviously, tidal currents are proportional to the tidal range; therefore there will be less current around 1st and 3rd quarter, with the highest currents being near the full moon and new moons.

Charlie

 

[Jonathan]

the tidal streams then ask the harbour master - they'll have a copy but if you are regularly diving in the area it will be worth the money in the long run. If you are going out of a marina why not make friends with a yaughty....

Jonathan

 

[Doof]

So what's this tide dial thing on my watch all about?

It seems pretty useless to me, since no matter what I turn it to, nothing seems to happen. Could the dial on my watch be broken? It also just gets spun around to different settings all on its own.

 

[Charlie99]

Doof once bubbled...
So what's this tide dial thing on my watch all about?

It seems pretty useless to me, since no matter what I turn it to, nothing seems to happen. Could the dial on my watch be broken? It also just gets spun around to different settings all on its own.

If it runs like an hour hand, but loses (runs slow) about 25 minutes per 12 hours, then it is just an indicator that runs in phase with the moon (actually, M2 main lunar semidiurnal constituent).
In most areas with 2 high tides and 2 low tides per day, this will get you about +/-1 hour accuracy. Synchronize the dial to high tide at full moon if you want to minimize the errors.