Timing the Tide

[carbon]

I could use some opinions. If you are doing a beach dive around the time of a high tide, and you don't want to get thrashed too severely on either the entry or the exit, is it best to:

1. Time your entry at the moment of high tide?
2. Time your exit at the moment of high tide?
3. Time the high tide moment to occur in the middle of the dive?

Thanks,
Carbon

 

[scottfiji]

I could use some opinions. If you are doing a beach dive around the time of a high tide, and you don't want to get thrashed too severely on either the entry or the exit, is it best to:

1. Time your entry at the moment of high tide?
2. Time your exit at the moment of high tide?
3. Time the high tide moment to occur in the middle of the dive?

Thanks,
Carbon

to avoid getting thrashed, its best to do the following:

- go when the surf is very low
- go to a sandy beach, not a rocky beach
- if its a sandy beach, the tide doesn't matter, imho
- if its a really rock beach, you want to avoid high tide
- whether you exit or enter at high tide, I don't think it matters at all, its still around high tide, and the tide predictions are not 100% accurate anyways

- from a scientific point of view, if I had to pick one of your 3 choices, of course i would pick #3, but I think the differences between 1 & 3 are irrelevant

Scott

(note - you can also skip all the above advice, and dive anywhere, with any surf, at any time. you need good entry/exit technique, which takes alot of practise. there are lots of separate threads on that technique).

 

[mccabejc]

Hmmm....I would agree with Mr. Fiji in part, and add that since the tides in SoCal can vary fairly significantly (usually between 0 and 6 ft.), that, along with the variations in bottom contour of the different beaches, might ultimately affect the "thrashability" index quite a bit. Depending upon the bottom contour, as the tide changes the entire appearance of the surf zone (where the breakers break) can change significantly, making an entry/exit either easier or more difficult.

For example, at low tide, if there is a shallow reef or the contour of the sand bottom gets shallow just off shore it may result in a long surf zone to maneuver through, due to waves breaking when they hit the shallow spot. But when the tide comes in, the water over that spot may become too deep to cause waves to break, and the surf zone might become much shorter and easier to maneuver through when the lull hits.

Or, maybe there's a steep drop off right at the shoreline, leading to a long, gradual slope out past the breakers. At high tide you might get very powerful shorebreaks and a short surf zone, and at low tide you might get a long surf zone with gentler breakers.

I guess the answer is "it depends": on the specific contours of the beach, status of the tide, and size of the incoming waves. But my guess is that, in general, high slack tide is going to result in a shorter and easier-to-maneuver surf zone, minimal currents due to tidal changes, and even better viz.

In my experience, a good thrashing is more likely achieved when you don't first watch the sets and time your entry/exit for a lull, and instead just enter or exit as soon as you get to the water. What I call the "head in the sand" approach.

That's a pun or somethin'. Get it?

Anyway, I would say that a majority of divers don't stop and time the sets, or even watch for the telltale signs of any big incoming sets breaking out on outside reefs/rocks/etc. before entering. As Scott mentioned, if you do it right you can minimize the whupin' you get on entry/exit.

 

[James S]

"- if its a sandy beach, the tide doesn't matter, imho
- if its a really rock beach, you want to avoid high tide"

The tide always matters, regardless if it is sandy. As water moves, you will find surge, the bigger the swing ( high vs. low) the more surge you will find. Try to dive during the period of slack tide after the high and surge will be reduced ( and vis will be better ).

Regaring the issue of avoiding a rocky beach at the high, it really depends on the beach. There are many beaches where the high will allow you to swim over rocks that you would otherwise have to walk through.

Mccabejc is right on with his statement of "Anyway, I would say that a majority of divers don't stop and time the sets, or even watch for the telltale signs of any big incoming sets breaking out on outside reefs/rocks/etc."

Watching the water for a few moments will tell you alot about what is going on out there and it is wise to hang out for a little while to get a pulse on it. Learn how to surf and you will become an expert on reading the water. Happy diving!
\
James

 

[mccabejc]

As water moves, you will find surge, the bigger the swing ( high vs. low) the more surge you will find. Try to dive during the period of slack tide after the high and surge will be reduced...

Technically, I think "surge" is a function of wave action more than tidal variation. Big waves with long wavelengths in shallow water result in large back and forth motions.

Normally, waves in deep water produce circular motion of the water as the wave passes by. In shallow water, however, that motion becomes more and more "flattened", and the diver feels it as surge, where he/she moves back and forth as waves pass overhead.

Occasionally, that "back and forth" motion will result in what scientists refer to as "hurling".

 

[scottfiji]

"- if its a sandy beach, the tide doesn't matter, imho
- if its a really rock beach, you want to avoid high tide"
James

whoa, I had a big typo there in my post.

I meant, if its a rocky beach, you want to avoid low tide. (not high tide, high tide is the best time).

I stand by my other statement though, if its a sandy beach, I don't think the tide is a significant factor regarding getting thrashed by the surf. Surge and vis are separate topics.

 

[ScubaSeanMaui]

I just dive when it's a good time. If the tide is ideal, great! Places like reefpoint have a rocky bottom that you can easily twist your ankle on so you'd want to dive it with a higher tide... My last dive with Claudette at 3 fingers had the vis improving in just 1 hour and the temp going down by 2 degrees. I bet the tide was comming in bringing in colder water which was more clear.

I just wanted to say that the swell is your main concern in regards to entry and exit!

 

[James S]

"Occasionally, that "back and forth" motion will result in what scientists refer to as "hurling".

Thanks Mccabejc, I knever knew the correct word for that! So what is it when there is a big swing ( 1.0 low going to a 5.8 high for example) that creates the surgy movement when there are no real waves? I've been pushed aroung pretty good on days that had no real swell ( if there was...I'd have been surfing!)

 

[scottfiji]

I just wanted to say that the swell is your main concern in regards to entry and exit!

Ditto

 

[mccabejc]

So what is it when there is a big swing ( 1.0 low going to a 5.8 high for example) that creates the surgy movement when there are no real waves?

Tides increase and decrease slowly and continuously, over hours as the earth rotates, so there's really no "surgy" aspect to them. For example, today the tide is at 2 ft. at around 3pm, then builds to a high of 6 ft. around 9pm. That's 4 ft in 6 hours, or about 8 inches per hour. So between 3pm and 9pm there's pretty much a constant, uni-directional raising of the water level by about 8 inches per hour. That can result in some constant current flows in one direction for a few hours or so, but the back and forth surge every 5-10 seconds or so is a function of the waves passing by.

Keep in mind that what may look like no real waves doesn't mean there are no waves. That's why a tsunami may be barely noticeable in mid-ocean, but as it gets into shallower water it may build up to a 20-30ft wall. As I recall, a wave won't rise up on the surface until it gets into water that's shallower than about 2 times the height of the wave. Which means that a 3 ft wave coming to shore might not be visible on the surface until it gets to where the depth is 6 ft deep or so. But there's still a 3 ft wave passing by, causing surge (depending on how deep you are).

As a matter of fact, last weekend when we were at Leo Carrillo, we had some dive floats anchored at 15ft depth, and there were some 5-6 ft breakers coming in. Those waves weren't visible on the surface until they got to almost exactly where the floats were. So that's a depth of a little over twice the height of the wave. Ballpark, but it gives you some idea. And there was surge-a-plenty out there (which, BTW, I heard did result in some "hurling").

If the surface is like a lake, and no waves breaking at all, you might feel a constant, uni-directional current (due to winds on the surface, tides, etc.), but I doubt you'll feel any back and forth surge.