In the last work­shop, we talked of pho­to oppor­tu­ni­ties in our back­yard, one of which occurs when there is a “minus tide”. Essen­tial­ly, a minus tide is a rel­a­tive­ly rare, very low ocean water lev­el con­di­tion that expos­es a large amount of reef or ocean bot­tom. The coast here has a vast amount of shal­low reef that, at a very low tide, traps many marine ani­mals and expos­es under­wa­ter plant life not nor­mal­ly seen while walk­ing on the beach dur­ing reg­u­lar tides.

I found this more tech­ni­cal expla­na­tion on the inter­net:

Jeff Ren­ner
What’s a minus tide?
A minus tide, also some­times called a neg­a­tive tide, is an unusu­al­ly low tide. Tide ‘heights’ are ref­er­enced to a base lev­el set as zero. This lev­el, called the ‘datum’, is the same lev­el used to ref­er­ence water depths on NOAA nav­i­ga­tion­al charts.

Usu­al­ly, low tides still remain a bit above zero, often a foot or two above. But the swing from high tide to low tide lev­els is great­est when the sun and moon are either on exact oppo­site sides of the earth, or espe­cial­ly when they’re on the same side of the earth. This cor­re­sponds to a full or a ‘new’ moon. The grav­i­ta­tion­al ‘tug’ by both the sun and moon pull water toward them. As the earth rotates under the oceans, high tides occur when that part of the earth is fac­ing either the moon or sun (or both). Low tides occur about six hours lat­er, when the earth has turned nine­ty degrees away from either of those ‘bulges’ of water.

Sun­flower Sea Star

This is indeed a pho­to oppor­tu­ni­ty to cap­ture a wide vari­ety of sea life pro­vid­ed the light is right and you are very care­ful with your equip­ment. Of course, you must con­sid­er the pos­si­bil­i­ty of drop­ping your cam­era in the water. Even if the strap is secure­ly around your neck, the rocks are slip­pery and if you fall in, your cam­era is going with you. These are things prob­a­bly obvi­ous to you but did not occur to me until I got out there for the first time.

But, if you are adven­tur­ous and except that risk, here are a few tips.
- Water proof boots help you get around eas­i­er and give you a bit more con­fi­dence.
- This is a good place to exper­i­ment with a polar­iz­ing fil­ter which can reduce reflec­tions on the sur­face of the water and pro­vide bet­ter pho­to­graph­ic access.
- Polar­ized sun­glass­es will also help your vision.
- Some kind of a reflec­tor can be used to illu­mi­nate the crit­ters hid­ing in the cracks or pro­vide more direct light when the sun is low.
- I find a tri­pod to be a hin­drance but you may want to try one if the light­ing is poor.

When are these tides? Well, there are 2 low tides every 24 hours, but the times vary. You just need to know what time they hap­pen and how low they will go. And you don’t nec­es­sar­i­ly need to wait for an absolute minus tide. Look for any tide near 0 and take a walk to the beach with your cam­era.

Click here to go to the dai­ly tide chart adjust­ed for Half Moon Bay. The chart shows the tides 2 days at a time. Scroll down to find more search options and a link for the entire year. I see that that the minus tides for August and Sep­tem­ber will most­ly be between 1am and 5am, when they do occur. Octo­ber and Novem­ber have some low tides on some late after­noons. The first week of Decem­ber is look­ing good for some ‑1.50 foot tides.

Check out pho­tos oth­ers have tak­en. Click here to go to Flickr pic­tures tagged with the words “fitzger­ald and marine” which show many pic­tures from the Fitzger­ald Marine Pre­serve in Moss Beach. The pre­serve is eas­i­ly accessed and very pop­u­lar dur­ing these low tides.

Click here to go to a tide pool group in Flickr.

The Half Moon Bay Review post­ed an arti­cle about the Fitzger­ald Marine Pre­serve and how it recent­ly gained enhanced pro­tec­tion sta­tus, a good thing with the state park clos­ings loom­ing over our heads. Click here to read it.

Well, that should keep you busy for a bit. Have fun and take some pic­tures!