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Magic of Minus Tide

Magic of Minus Tide

May 1, 2021
For a brief time during minus tides, the hidden mysteries of the reef are revealed. Join us for an exploration of the intertidal zone!

Explore the intertidal zone to discover giant green anemones, purple sea urchins, and various species of crabs. Hopefully, we will also come across tiny, beautiful nudibranchs.

We meet bright and early at the parking lot for Agate Beach in Bolinas before the tide has turned, and take a brisk walk along the beach to Duxbury Reef. Herons, egrets, black oyster catchers, and other birds will be on hand for the low tide buffet spread. We head directly to the infra-littoral zone where we will find giant green anemones, purple sea urchins, and nudibranchs. We work our way back to the mid-littoral zone with purple shore crabs, California mussels, and perhaps ochre stars that are just starting to recover after the devastation of wasting disease.

As the tide turns we explore the rockweed zone with lined shore crabs, rockweeds, and black turban snails, and finally the splash zone with barnacles and periwinkles. You will leave with a greater appreciation of the world below the waves, where hooked slipper snails live on black turban snails, seaweed limpets live on the stipe of feather boa kelp, and algae find a home in green anemones, giving them sugars in return for a safe place to live.

Be prepared for a long walk, some of it on slippery seaweed covered rocks, and for getting wet feet!

Wendy Dreskin has been teaching the popular class Meandering in Marin at College of Marin since 1998 and Point Reyes Field Seminars since 2005. In recognition of her work inspiring both children and adults, she was awarded the Terwilliger Environmental Award and inducted into the Marin Women’s Hall of Fame.

Photo Credit: Linnea Hendrickson


-We will be meeting at the Agate Beach Parking Lot in Bolinas

– Please arrive 10-15 minutes early to check in, class will begin promptly at 8:15 to take advantage of the tide

– Refunds available for all classes 7 days in advance of the start date, after 7 days and before 2 days, participants can credit their class for a future date. All requests before 48 hours in advance will be declined. For COVID cancellation policy, see below.

– Please follow the parking instructions for the facility used that day

– Please provide an email you check regularly for updates and reminders about your class

– Registration is required online prior to the event in order to maintain class sizes

– Sales end 48 hours before the start date.

– Waitlists are available when the class sells out

What to Bring:

Footwear: Everyone has their own idea of footgear for a minus tide. If you choose high rubber boots, be sure they have good tread. Salt water will ruin leather boots so leather hiking boots are not recommended. The instructor suggests neoprene socks and old running shoes with tread. Some people use wetsuit booties.

Day Pack

Lunch Bag (optional)

Warm Variable Weather Clothing

Water Bottle

Notebook and Pen/Field Journal

Eventbrite Confirmation Email

Binoculars (Optional)

Camera (Optional)

About the PRNSA Field Institute:

The PRNSA Field Institute offers hands-on environmental education classes throughout the year that foster enjoyment of Point Reyes National Seashore. Our classes are led by expert instructors, who take you out of your everyday life and into the natural world. We host a variety of classes about the arts and sciences and have something for everyone. You can reach the Field Institute at (415) 663-1200 x304 or by email at

Interested in becoming a member of PRNSA? Click Here!

Interested in becoming a PRNSA Field Institute facilitator? Want to take classes for FREE while helping out a great cause? Give us a call!

Are you an outdoor educator or artist who would like to teach a PRNSA Field Institute class? Shoot us an Email!

For any questions, please email us at

COVID-19 Field Institute Guidelines

In accordance with Marin County guidelines for public health and safety, we will require all participants to respect the following COVID-19 procedures:

Perform a health self-check before coming to class using the CDC Symptoms of Coronavirus as a guide

Do not attend class if you are experiencing COVID-19 symptoms, suspect you have been exposed to the virus, or are suffering from any other flu-like or respiratory illness.

Participants exhibiting signs of respiratory illness may be asked to leave class

NOTE: Refund policy exceptions will be made for participants cancelling last minute due to COVID-19 infection or symptoms. Please contact us in this case.

During class all participants will be required to do the following

Wear a protective face covering

Maintain a 6 foot physical distance from other participants not belonging to your household

Bring your own food and water

Current group sizes are limited, there will be no physical contact or sharing of food and drink, and no shared physical equipment or materials unless they are sanitized before and after use, and used by only one person for the duration of class

Thank you for your cooperation in following these guidelines to help keep everyone safe.