Recreational Safety Home


Life Guards, Hypothermia. Personal Flotation Devices


Seas and Swells
Wave Size
Tide Pools
Playing in the Spray Russian Roulette - Morro Bay Style


Boating in the Bay, Boating in the Ocean, Morro Bay’s Rough Bar, Fog, Suction


Falls, Falling Objects, Stinging Nettle, Poison-Oak, Mountain Lions, Ticks, Rattlesnakes, Poison-Hemlock


How Far Can Waves Reach, Mortality Statistics, Off The Road Vehicles, Mountain Biking, Miscellany



The NOA maritime forecast includes a statement like “NW WINDS 10 TO 20 KT WITH OCCASSIONAL GUSTS TO 25 KT. WIND WAVES 2 TO 4 FT. NW SWELL 7 TO 9 FT AT 11 SECONDS.” This means that local winds have stirred up a 2 to 4 foot chop. In addition there are significant waves from previous storms, coming predominantly from the northwest (the Aleutians) hitting still objects every 11 seconds. The average height of the biggest third of waves is expected to be somewhere between 9 and 13 feet.

One problem created by waves of this ordinary-for-the-ocean size is that the person in the water in a man overboard situation is hidden most of the time from the view of the crew of their boat. Another problem is that the stern of the boat plunges up and down dangerously to the person in the water, who may be weakened, obtunded, or even unconscious because of hypothermia. Stern ladders are often unusable, and rescues are usually attempted from the side of boats, because of this.

Seas and Swells
Ocean storms produce “seas”, choppy wind waves up to 50 feet high that break repeatedly, amidst much spray. After each storm is over, the seas change into smooth waves called “swells”.

Swells produce the most familiar kind of rocking of boats at sea. They transmit the power of storms in the direction the winds were blowing, unabated, all the way across the ocean.
Traveling at speeds of up to 20 mph, it takes 4 days for the faster large swells to reach us from the Aleutians; and a week for them to reach us from New Zealand! Once here they crash, eroding the shore.

Wave Size (Giant Waves, Rogues, Sneakers, or Freaks)
Waves vary in size. Large waves tend to come in a series, or “trains”, alternating with smaller waves.

Another way to characterize wave size is statistical. According to Jack Williams in “From Ripples to Rogues…” (dtmag.com/Stories/Dive%20Weather/09-00-weather&waves) “One wave in 23 will be twice as high as …average…one in 1,175 will be…three times the average height, and one in 300,000 is four times the average.”

When you walk along a beach, you’ll observe the sand is usually wet above were the waves are reaching. That’s often because the sand has been wet by larger waves, and has not yet had a chance to dry.

How about those less frequent, but really big waves? Here are three firsthand accounts:

A Close Call: An Army sergeant was letting his 5 year old son run on the beach. All of a sudden there was water everywhere. His son was floating. He sprinted across some cement parking bumpers piled on the beach, lunged, and just caught the boy’s arm, who otherwise would have been swept into the sea.

Is This A Car, Or A Boat: A friend was sitting in their car at the big Rock Parking Lot, when a very large wave came over the rip rap, between the bumper logs, and floated the vehicle 12 feet.

That’s How They Got There: I’d wondered how big logs got hoisted so far up on the local beaches. One day I was standing on the observation deck at the south end of the Cloisters walkway, when I noticed the sea advancing over the beach. The water covered 50 feet of wet sand; 300 feet of dry sand; flowed behind the fore dunes; floated a tree trunk that was a foot in diameter and 10 feet long; and spun that tree trunk 180 degrees!

Giant waves have been reported at sea as well as at the shore. Steep waves a hundred feet high have probably plunged through the decks of vessels, sending them straightaway to the bottom.

Tide Pools
Two popular local activities come to mind at this point. One is visiting tide pools. Clearly this puts you at risk from large waves.

Family tide pooling. The swell originated near Hawaii.

Experts agree that should you see a big one coming you should grab the nearest rock, hold on tightly, and take a deep breath. The common mistake is to stand up and run. If you do that you are likely to slip on the slimy rocks, fall, and get hurt; then the wave hits and tumbles you over some more rock, hurting you some more; after which you are swept into the frigid surging deep water adjacent to the rocks you were standing on. (At that point it is URGENT to get back up on the rock!)

Playing in the Spray
The other popular local activity is watching the surf break on a day when the waves are forecast to be 18 to 22 feet high. The photograph, by local resident August Phillips, shows a visitor making two mistakes. . The ground around her was clearly wet, so she was standing closer than I recommend. Then, she tried to run across the wet rock; she should have just scrunched down until the spray stopped. She spent the night at Sierra Vista Hospital with bruises of an arm, leg, ribs, collarbone; and a mild concussion.

I say: “don’t play in the spray; stay 50 feet away”. Watch the spray, but stay fifty feet back from wet ground. Keep in mind, too, what to do if despite that precaution you still find yourself waist deep in a particularly large wave. And, supervise your kids!

Continue to Page 2, Waves

All content copyright Dr. Curt Beebe. Please do not use without permission.